If the panel gap is not "neat", which is not the same as "small", then it looks bad.
I don't know if I could find a source, but it would probably be something like Forbes in the '80's: Lee Iacocca (of Chrysler) said that they learned from Japanese collaboration that if they made their gaps wider, then they appeared neater because they appeared parallel. And it was cheaper to make a wider gap, and it was easier for QA to pass the cars. Otherwise the cars would have to be whacked with mallets until the narrow gaps looked right, and that slows the line, and that indirectly adds cost.
[This doesn't mean that the Japanese collaborators were making huge panel gaps on their own cars, it simply indicates that Iacocca('s people) got a certain idea from them]
You'll care about panel gaps when there's snow in your trunk or blowing around in your cabin. You also might care that your car looks like it was in an accident and repaired by an amateur.
In a way though you're right - no one cared about panel gaps until Tesla came along because until then even the cheapest of the cheap manufacturers were able to get that right.
I use to read about the panels gaps on the Tesla and thought so what? Then as more Tesla's started to show up on the road and I saw what they were talking about I finally get it.
The cars looks like they were in an accident and had their body panels poorly repaired/reassembled.
