Are the offsets on the oem 1991 set up like that for reasons of handling or are there any other reasons? With larger wheels the offsets tend to push the wheels out more- is this aesthetic or a there any handling benefits?

i find it all confusing. I have driven my car with wider offset 17/18 wheels and it drove terribly in comparasin to the oem 15/16 set up.

most posts and info seem to focus on how light wheels are or how good they look. Please inform me beyond this point!