The reason I do that is because I can ascertain the quality of the clothing and determine that, despite them being cheaper and used, they are just as good if not better.
I'm sure there's a lot of parents who assume, incorrectly, that a used and relatively clean car seat is just as good as a new one. So, they save a few bucks because why not?
Unfortunately when a new child arrives finances tend to be at a minimum and this deep discount works out as a almost always better than nothing and for super cheap.