Seeking to understand speaker phone use in public

I'm traveling with family this weekend in a touristy place and have been out in public in crowded areas. I am really shocked by the number of people who have loud, personal conversations on the phone in speaker mode. This ranges from walking down the sidewalk, to in line for washrooms, to seated restaurant dining.

I've heard people say that it's because the phone speaker breaks (for their ear) but I've never had that happen in all the years I've destroyed phones and never had a friend or colleague say that happened. Other people say it's because the glass is cracked and they worry about cutting their face, etc.

My personal bias is this is inconsiderate but then I ask myself how is it different from talking to a person next to them, say. I'm willing to be change my mind here.

People who do this, please explain what's going on so I can sleep at night. :)