Why is living at home so bad?

It's not necessarily. I love my parents (I mean mum is dead now but I love and miss her a lot, we got on really well when she was alive) but I left home as early as I could and stayed away not because I didn't love my parents but just because I really wanted to figure myself out and find my own routines and live on my own, and I was really lucky that my parents were very supportive of that. I genuinely think for me having that space and autonomy gave me a better relationship with my parents than I would have had if I had stayed at home. I would have been fine at home, but sharing with housemates is very different to sharing with your parents.  But loads of people live with their parents and it's great for them. They get more time with their parents in person, sometimes you can save money, sometimes you get cooked for. Can be a sweet deal.  Other times living with your parents means you're caring for them, and that can be hard. Or you might have abusive parents or a bad relationship with them for various reasons. So it can be very hard but even if you don't, in my case as much as I love my parents I would definitely have felt the shift in dynamic and sense of losing my independence sharing a home with my dad rather than my partner or friends.