Maybe you can't with Max contracts due to the max cap % you can pay out and then the annual raise restrictions and all that, but you always could with sub max contracts. You can also just split up the contract evenly, like Jarrett Allen's deal. He gets 100 mil for 5 years and every year he gets 20 mil. Which is in practice a regressive contract where his % cap hit decreases year over year.

What you said is interesting in that it doesn't seem to happen that often, where you could butt up against the cap one year, get relief for future years with a regressive contract. Maybe it's just the belief in kicking the can down the road and counting on cap increases while maximizing current rosters.