Why is making a phone call on speaker in public so hated? Seems to me the only difference between this and a normal conversation is that one of the voices is disembodied

i'm a zoomer software dev from georgia usa, im gay, i like art and music and math and programming
USDA plant hardiness zone 7a/6b
Why is making a phone call on speaker in public so hated? Seems to me the only difference between this and a normal conversation is that one of the voices is disembodied