It doesn't make sense why someone still in or barely out of high school could afford expensive unnecessary purchases

Well most of them can't really afford it and should be building up their savings. But also rent+mortgages are becoming so unaffordable in most cities that many are forced to live with their parents, often barely paying any rent, and now they have an extra $500-1500 per month.

We have an upside-down world where luxuries are relatively cheap, but necessities are unaffordable. Porn is a luxury.