The climb up to 3500 AGL can be made more beneficial by using this time for the student to practice precise climbs and climbing turns, ready for the circuits exercise that follows stalling. If the instructor is just sitting there looking out of the window then you are probably justified in feeling it's a bit of a waste of time. (In the GFPT I use this climb to cover the IF requirement.)
I have been doing this job long enough to not deliberately stall an aeroplane below 3500". That is why it's in the ops. manual as an SOP. The scariest stall I ever had was a wing drop in a Warrior, of all aeroplanes, where the student froze and applied full opposite aileron. It took 2500" to recover. (However, we run a low-level course where you do stall recoveries at 300', if you're interested!!)
It would be a tad naive to think that a wing will never drop and that we live in an ideal world where the students never touch the ailerons or rudder in a stall. And aeroplanes that you think you know well can turn around and bite you sometimes. They don't like flying slow.
Just a hint in this area...when recovering from a stall, if you teach them to apply forward pressure in the middle of the control column, like beeping the horn in your car, they are far less tempted to use aileron.