> The default font shouldn't be about aesthetics, it should be first and foremost about usability.

The thing about usability is that it's both objective and subjective, and one can argue that aesthetics is part of usability. For example, I find writing code much more pleasant with Comic Code font, and I can imagine that there are other people that would hate it.

Sure but I think we could agree it looking nice ranks lower than being structurally more difficult to read for people? If there were a freely preinstalled option that was both sure but given the choice between functional and aesthetic readability wins hands down.