Supposedly it has something to do with typewriters malfunctioning when placing the period or comma outside. Which makes it even more annoying that it is an adopted standard.

I'm not sure I believe about typewriters. It doesn't really make sense to me as the characters are still adjacent to the quotes. So I wouldn't think shifting them would help with jamming the keys.

I do suspect though that it's probably related to aesthetics and/or mechanical issues associated with lead type.