I am at once awed by the level of work that goes into a really good typeface, and also astounded that this still seems to be a difficult sort of terrain that people are not just willing, but positively excited to summit. Why go to the trouble when your font is only going to be seen by a small number of people and used by even less? Are you really having any ideas that haven't been had already in plenty of other fonts? Will your extra 0.001% tweak to readability make life easier for 0.001% of people that read something written in it?

There are font nerds just like there are nerds for a million other things. Their passion is fonts, so yes, they will spend that amount of time on it.

Tiny changes to letters can have a big impact on how text blocks are perceived, fonts are utilitarian, but they're also design tools.