You need a history expert for this one. I want to say theft deterrent, and possibly different voltages for niche applications. Also Need Flanders Leftorium.

That’s totally fair. I happen to know a lot about this topic and didn’t read the article at first, and I also meant OP as in whoever posted the article, not you. I could have been more helpful here, sorry.

This article is dogshit, and those are not the current exemptions. DOE revised the definition of a general service lamp on 2022 to include the majority of reflectors. The rest have miniscule sales and have technical limitations that make LED replacements difficult. It’s not a lot of exemptions. When was the last time you bought a left hand thread or a colored incandescent lamp?

OPs list is wrong, that’s why. DOE revised the definition of a general service lamp in 2022 to include the vast majority of reflector lamps. Bug/appliance/left hand thread/etc are all sold im tiny numbers and therefore exempt.