Frown upon

Why are trailers/mobile homes so frowned upon? My cousin recently got a brand new one with a slick high end interior design, appliances, and it’s large (1,500+ sq ft). And it’s very affordable compared to an apartment and definitely in this housing market. So, my family still say, she lives in a trailer park and I’m just confused how is this a bad thing. She owns the trailer, it’s new, and looks great inside and out. It’s hers and a great starter home, too.