Appropriate clothing

Hi, I'm after some advice regarding my 20 year old son, who was diagnosed with ASD last year please. Like many others, he prefers comfortable clothing like joggers and soft jumpers and tops etc. He has favourites that he will wear day after day. He will put them out for washing eventually. He has some new clothes, equally comfy and will wear them but still prefers the old favourites. The main issue is, some of his joggers are not long enough and finish just above his ankles, and they look quite old. I have spoken to him about maybe getting some more new ones that fit but he doesn't see there being a problem. He feels comfy and that's all that matters. I notice people giving smirky looks when we are out sometimes and I just want to protect him from any negativity. He says it doesn't bother him. So really, I guess I'm wondering, do I just accept that he feels happy with how he looks and ignore others or do I try to explain how it looks, which I have been reluctant to, in too much detail, as I don't want him to feel self conscious. He's such a lovely young man and I just want the best for him. Thanks so much x