Many years ago, as an IFR flying instructor, I asked Melbourne ATC for a surveillance radar to 27 Melbourne. It was meant to be part of the students instrument rating training. Too busy, said ATC.
No problem so we tried the next day. Too busy, says ATC.
Third day I phoned ATC to give plenty of notice and asked what's the chance of just one lousy surveillance approach? Never happen, said ATC we are always too busy.