I read somewhere that T12 and T8 fluorescents where introduced around the same time.  If this is true how come T12s weren't banned untill just reacently if T8s are more efficient?  Was it because T8s were more expensive?  If so then why make them?

If to judge according to the EU, they ruled that tubes more than T10 will be banned, meaning 40W T12 is illegal, but 8W T5 is legal, and 15W T8 is also legal, and 40W T9 circular is legal!!! The EU need to get lost!!!
The 18W, 36 and 58W T8s are retrofit lamps for T12 lamps on their preheat ballasts, and are invented in the 80'.
The american F32T8 also invented in the late 80'. These are the 15W, 20W, 30W and 50W T8 that invented with the T12.

T8 4' lamps for general lighting service are relatively new (introduced probably in the '80s, becoming popular in the late '90s). On the other hand, 4' T12 tubes have been around almost since the beginning of fluorescent technology. T8 technology is now "mature enough" in the eyes of the lawmakers that T12 can be phased out. Of course we know better, though!

Don't forget, too, that there are still a lot of T12 4' lamps available! The ban didn't affect all T12 lamps; only those that had poor CRI were phased out.

T8-size tubes and T12s were introduced around the same time, but modern T8s, like the F32T8 and F36T8 are relatively new.  The original sizes of fluorescents when they first came out were the F15T8, F30T8 and F20T12.  The F40T12 came shortly after.

Thank you very much for the info!

I believe the F32T8 came out around 1982 and Sylvania was the first to make them, here's a page from a 1982 Sylvania catalogue showing a early F32T8 when they came with black end caps.

The F32T8s originally ran on magnetic rapid start ballasts similar to T12s and sometimes you'll still come across a old installation of T8s that are rapid start. I believe the electronically ballasted T8s we know today only took off sometime around the 90s.

all the idea of banning lamps is fairly recent. The T8 might have existed for long time yet nobody thought of banning the T12

That is good to now, thanks.