then why dont some wear jeans if not for my reason
Flatbush, there is a big difference between saying you CANT wear jeans and saying that its not how you want to present yourself.
Many people (as said above) don’t wear jeans because they think they are too casual. This is a far cry from “I think a male Jew who wears jeans would be not be following the above said halacha.” Do you understand the difference?