Depending on the community..jeans are very street-like and casual…wearing the jeans adds to a certain look that many frum people try hard to avoid….
I’m not saying they are bad or the jean wearers aren’t Torah abiding but the majority of the frum community emphasis to maintain a certain dignified look and appearance
—’cause whatever argument you have to refute this in the end of the day the way you look is the way you’ll be looked at!