Containers run with a tty attached but no console on the other end and then trying to read the logs, for starters. Additionally, as mentioned, conflicts with the user's color scheme or even the program's. Further, it's possible to do this without the help of run0, so I suspect users already doing that are going to get their colors messed up and be annoyed. For example, prod machines are usually red, and running as root on a prod machine is royal purple. If this is used, seeing a red background instead of a purple one is likely non-desirable.