It's because they are hackers. If they add you or even just light you, you might report them and they will get banned from the game. That's why they don't light people. It's sad but it's like this because there are people who will report all hackers just because, even if they are just chilling like this guy.
I still wish they would put the delay on the players side instead of the server like in other games so others could actually hear what youre playing and not hear a bad version even if that means you will have a bit of delay when pressing notes
