I non-disposable ones to keep cold and acidic drinks from washing over my sensitive teeth.

There are plenty of people with motor issues where a straw really does mean having the freedom to drink on your own. Also, in the US, ice is more popular to add to your drink and a straw means not getting blasted with a bunch of ice.

Kids love em. Although I am impartial to a straw into a cold milkshake or mango smoothie on a hot day.

in the US most people drink stuff with a ton of ice. it stops the ice from hitting your mouth/teeth when you drink. it's also easier to drink in a moving vehicle with a straw and not risk stuff splashing all over you