[bleucamaro]

In OEM application, its fashion but is there to keep a car with appealing proportions. New cars are huge, and I believe part of it is because of safety standards Bumper and headlight heights, and higher window sills give higher belt lines. If you put anything smaller than an 18” wheel, it would look funny and out of proportion.

In the aftermarket, the DONK craze is driven by the same geniuses that created spinners.

I recall reading an article a long time ago that said 17” wheel is the best balance between strength and weight because as you go larger, you lose hoop strength and to compensate you need to add material. Plus to maintain the same overall diameter tire, the sidewall needs to shrink to accommodate a larger wheel, reducing its shock absorbsion qualities.