The use of gloss paints gives you an option. The super wet look of a clear overcoat is too wet for some subjects. There is a difference in look between a clear glosscoat and a natural gloss paint finish. This is particularly true for older cars that were painted before the factories started using clear coats. Something like a '49 Ford looks funny with a glosscoat unless it is a custom.
Doped civil aircraft also look funny clearcoated- doped surfaces were glossy, but not super gloss.