It’s absolutely infuriating. I don’t mind people talking around me but the type of painful noise a phone speaker puts out is just plain irritating. It’s completely rude and inconsiderate to be on speakerphone in public. I see it all the time on public transit and in cafes. You also often see people play videos or games (especially kids) without headphones on airplanes - although now airplanes are cracking down on that.

I think the issue is a general increase in anti-social behavior - but part of it is definitely cultural. As an example, I never see Japanese people on their speakerphones in public. Some other cultures seem more likely to view it as acceptable (or just care less about how they impact others). I’ve also noticed that elderly people are much more likely to be on speakerphones taking calls with the volume at max, so personally I think there’s an age aspect too.

I visited the US for the first time in the early 2000s, and the amount of people having their call on speaker in public was really jarring.

Here in Norway it's still quite uncommon, though back then nobody did it.