Why do some people say it’s a bad idea to live with friends, especially best friends?

Everyone situation is different. My dad says that it’s a bad idea but if I want to do it going ahead and he can’t stop because I’m an adult. I guess I’ve been hesitant to like be roommates with her because I don’t want our friendship to be ruined. She’s probably gonna tell me that’s a lame excuse to not be roommates and she really wants me to live with her because I’m the only one that she trusts.