Because as you get older over time you can observe how this kind of "content" messes up young peoples' expectations about the average human body, instills a shallow and superficial mindset about relationships, and generally does absolutely nothing of value for anyone except the parasite who is manipulating ignorant or desperate people using sexuality for profit.
It’s strange how people will readily admit that advertising can cause unhealthy eating habits but sexual content can never cause unhealthy sexual habits.