Here in the US, I can only think of 1 or 2 airports where you'd see ALT CNST in the climb, so it's really not an issue here. I understand Europe to be a bit different though.
At the other end of the flight, some airports (eg MCO) may only have a single constraint. If you set whatever you want there, you probably won't be bitten. At airports like LAX though, there are 13 restrictions from T/D to the FAF. With busy airspace, and constant speed changes, the last thing I need as PM is to have to worry that the PF is gonna bust an altitude.
BUT, as long as it isn't against SOP, I keep my mouth shut.