Do you realize that original phones weren't used in public?
Until the cell phones became ubiquitous in the late 90s, most phone calls were made in the privacy of a home, office, or phone booth. Even phone booths that weren't enclosed were often off to the side in a designated area.
And even for the very short time in history that mobile phones have been common, nearly everyone agrees that being next to someone on the phone is annoying. See half the comments from
this thread as an example. This also applies to subway trains, coffee shops and restaurants, store checkout lines and bus stops, movie theaters and stadiums, and pretty much any place where you are in public and stationary.
I'm not saying all public phone conversation are annoying. I don't think the people that are walking down a street while on the phone are annoying - because they aren't next to anyone for an extended time. And I have seen people be polite about a quick chat on the subway. But in general, talking into a gadget in public when surrounded by other people is obnoxious.