I really don't think it's the inches that make the rim look like ass...
It's the design...
There are some 20" rims that look killer on GPs, some that look like round bricks...
After I mounted the 18"s on mine, & got used to them, I started seeing how someone could put 19"s on their car... I'm sure if I did 19"s I'd feel the same way... Next thing you know, I'm looking at 20"s
There's a GP here in Rockford with 22"s on it, car looks nice. (I wouldn't do it)
Just because most of us are gear heads looking for more HP, we shy away from heavy wheels...
If you are more interested in outward appearances & not worried about speed... Why not get some nice looking 20" rims?
If I was "showing" my car, on weekends... I'd get a set of 20"s for show.
I have 16"s for the front for the slicks. 17"s for the snow tires. 18"s for the summer tires...