It has never appealed to me at all. First, you usually don't know this person well (fwb don't apply, but that's a whole other bucket of worms). Therefore, you don't know if you can trust them, and why would you want to be that vulnerable if you have no idea?
Second, it seems unhygienic. You don't know them well, so you don't know their germs either. You could catch something. Why have sex with a person whose glass you wouldn't feel ok drinking out of?
Third, I wouldn't let anyone I didn't know really well, say, look through my diary. Why show off all your flaws and weirdness and quirks?
People can do what they want; it's their body, their life, but I feel alone in this.