Why are low pressure sodium lamps not used for street lighting in the USA and Canada?

The pure yellow light is unnatural, and obscures all colors. But they are used in a few places - sometimes under overpasses.

A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.

Two varieties of such lamps exist: low pressure and high pressure. Low-pressure sodium lamps are highly efficient electrical light sources, but their yellow light restricts applications to outdoor lighting, such as street lamps. High-pressure sodium lamps emit a broader spectrum of light than the low-pressure lamps, but they still have poorer color rendering than other types of lamps. Low-pressure sodium lamps only give monochromatic yellow light and so inhibit color vision at night.

LPS is unpopular probably due to color. Who wants to see a yellow light the makes anything with color look bad? With that being said, there is (was) a good amount of LPS fixtures here in California. San Jose up North was a big user of them. There's also South California which Murrieta and some other cities by the 215 as well as the 5 use due to being close to an observatory. Most of those on the 215 and the 5 got replaced. There's also a restaurant in Palm Springs I saw with 18w and 35w LPS lights!

LPS is unpopular probably due to color. Who wants to see a yellow light the makes anything with color look bad? With that being said, there is (was) a good amount of LPS fixtures here in California. San Jose up North was a big user of them. There's also South California which Murrieta and some other cities by the 215 as well as the 5 use due to being close to an observatory. Most of those on the 215 and the 5 got replaced. There's also a restaurant in Palm Springs I saw with 18w and 35w LPS lights!

California historically was an early adopter of low pressure sodium. The Golden Gate Bridge had 10000 lumen NA-9 lamps up until they were discontinued by GE in favor of high pressure sodium in the 1960s. These were the very early variety with a removable dewar jacket, and they used a UX4 tube socket as opposed to a normal lamp base. They might also have had an asbestos washer between the inner bulb and the dewar jacket, though I’m not sure on that.

Such a pity what California has turned into today. At one time it was known for beautiful scenery, but now it is only known as a “progressive” liberal wasteland of homelessness, where everything is banned.

They saw some use in my area. All the municipally owned expressways in Toronto used to have 180w LPS from the mid 70s onwards to the mid 90s when they started replacing LPS with HPS. The last of the LPS lights were changed out in mid 2006.