I'm particularly sensitive as there a lot of people that go to my university that go around like wearing cargo and carpenter jeans (not so much in the summer), along with like tye-die shirts and what not. And while its not like they are particularly jarring to me or anything, its just that these people also tend to just look really lazy, and come off as sort of lazy and slob-like. That is just the kind of image I get with the whole thing of not being particularly concerned about your appearance. I think you are confusing the difference between not being concerned at all about your appearance and trying to make it look like you at least tried to think about what you put on in the morning. If you just go grab your wardrobe in the dark and run with it, who is to say that it is unreasonable to view this sort of thing as laziness? Also, yes I would probably tell a spouse is they were wearing something terrible, and I have had it done to me before as well, and I was totally fine and appreciative of it.
Its not like I am condeming you, and it is not like I would particularly refuse to hang out or be seen with somebody who was wearing something that was only on the slighter end of atrocious (I have to do it all the time when it comes to my roommate), but seriously, if you don't think that you need to be concerned about the sort of clothes that you are wearing once you get out of high school, then I'd be interested into seeing what happens when you enter in the professional world, and need to make connections with clients, companies, and what not. Also its not like it is any less important to be looking decent in the club scene as well.