I sometimes struggled with two channels, then when I replaced my faulty analogue scope with a Rigol DS1054Z I had enough channels.
Maybe my requirements are unusual, I am a radio amateur who likes to build transmitters and receivers. The 4 channels enable me to check keying input, receiver muting, RF envelope, DC power switching to intermediate stages, etc. Yes, it can be done a stage at a time with 2 channels, but it's easier with 4 and at the price of a DS1054Z it's a "no brainer" for what I use a scope for.