I've noticed that the Americans take care about the power factor of their ballast more than any other parts around the world. In Israel for example, this subject is usually ignored, and I think that the European also don't take care so much about the power factor of their ballasts.
Why this is the case?

As an American, I... don't know the answer. I too, want to know why.

We like clean power factors? 

It's usually only a concern with larger (typically industrial) buildings since they have large motor loads and will get billed extra for low power factor by the utility company. Ironically most utility-owned street lights have NPF ballasts (at least here).

It seems most people here thinks Powerfactor  means full power lfluorescent lamp brightness it seems on here
But this not the case.  There are full power normal power factor balkast around.  Power factor all it does  is to make
Help keep power current in phase with voltage. 

yeah BALLAST factor and POWER factor are two completely different things. However, in the case of magnetic ballasts, LPF ballasts tend to have a lower ballast factor than HPF ballasts, likely to keep overall line current down, since a LPF ballast with a 1.0 ballast factor would have very high current draw (but wouldn't consume any more power than a HPF version with the same ballast factor).

I don't think it's just an American thing, I always include a PFC capacitor on my discharge lamps, if only for the fact that it makes the installation complete. I build display boards and it's important to me that they're correct. If the manufacturer of the ballast specifies a PFC, then a PFC it will get. Depending on what I have in stock, it may not be the exact value specified, but it will be as close as I can get it.

It's usually only a concern with larger (typically industrial) buildings since they have large motor loads and will get billed extra for low power factor by the utility company. Ironically most utility-owned street lights have NPF ballasts (at least here).

Maybe your utility has a separate street light circuit in the poles, which could get power factor correction through a centralized bank of capacitors rendering them useless in individual street lights (and in the process eliminate capacitor fault in street lights).

No the street lights are all powered right off the transformers that feed the houses. Same goes for underground; the lights are never on their own circuits except for utility-owned freeway lights, which are still wired directly off "pole pig" transformers, just on their exclusive underground circuit from the transformer onward.

The utility overcharges for street lights anyway so they definitely make their money back. They charge an annual rental/maintenance fee ranging from $50 to $175 a year depending on the wattage and then they charge the estimated kWh usage. They don't bill for 50, 70, 100, 150, etc watts either, they bill weird wattages that included ballast losses. So those wattages end up being something weird like 62, 85, 118, 173W etc.

the larger wattages (250 and 400) already have capacitors too, being CWA type. They fail often in the GE lights.

Yup.  We get a $70.00 street light surcharge once a year I think, maybe twice a year.  But given the fact that they do such a good job taking care of the lighting here and are quick to respond to service requests, I don't mind so much.  Now if I lived in an area with no street lighting, that would be different. 

I find ballasts with a power factor correcting cap work better and give more reliable performance. NPF 2lamp F40 ballasts seem to run like crap while their HPF counterparts are less likely to. I also prefer my lights to draw less current

Although I don't really know the major details as to why Power Factor is important, I can definitely say that HPF rapid
start magnetic fluorescent lighting, is what started it all in terms of my interest in lighting in general.

在20世纪70年代之前，我们中国的30-40W以上的荧光灯还是要强制安装电容器的，要不然供电局不给送电！

I find ballasts with a power factor correcting cap work better and give more reliable performance. NPF 2lamp F40 ballasts seem to run like crap while their HPF counterparts are less likely to. I also prefer my lights to draw less current

But that is not about the power factor per se, but about the ballast quality in general.
The good lamp operation is one consequence of a good ballast design, high power factor use to be just another such consequence. Or better said, when you want to make a good behaving autotransformer based RS ballast, the cheapest way to do that happens to inherently yield a good power factor.
It is only when you sacrifice the lamp operation quality to get further cost reduction, only then you get the NPF RS ballast.

But there is nothing to prevent the existence of a good operating ballast (towards the lamp) from being a NPF. A good example is a series choke preheat circuit.

No the street lights are all powered right off the transformers that feed the houses. Same goes for underground; the lights are never on their own circuits except for utility-owned freeway lights, which are still wired directly off "pole pig" transformers, just on their exclusive underground circuit from the transformer onward.

The utility overcharges for street lights anyway so they definitely make their money back. They charge an annual rental/maintenance fee ranging from $50 to $175 a year depending on the wattage and then they charge the estimated kWh usage. They don't bill for 50, 70, 100, 150, etc watts either, they bill weird wattages that included ballast losses. So those wattages end up being something weird like 62, 85, 118, 173W etc.

the larger wattages (250 and 400) already have capacitors too, being CWA type. They fail often in the GE lights.

Yup.  We get a $70.00 street light surcharge once a year I think, maybe twice a year.  But given the fact that they do such a good job taking care of the lighting here and are quick to respond to service requests, I don't mind so much.  Now if I lived in an area with no street lighting, that would be different. 

Jeez id do that if I could, last I talked with the local EMC they wanted $35/month for a 150w HPS DG cobra head on the utility pole so I didn't do it, makes me want to re-ask to see if I mis-heard them and they meant per year!