There are a number of reasons why your instructor will not like you doing flapless landings.
Firstly all students are a bunch of idiots who must be protected from themselves so everything has to be kept as simple and uniform as possible.
You will be landing flatter so may not see over the instrument panel
You may misjudge your glidepath and take out a few trees and cows on the approach.
Less flap means less drag so being a student idiot you may not control your speed.
Less flap also usually means higher stall speed so you may stall.
Using numerous landing configurations may mean that being an idiot student pilot you may forget which one you are using and use the wrong speeds.
As most training nowadays involves avoiding everything are you surprised?
Of course I dont agree with any of the above and think pilots should be trained as pilots not plane drivers
Pace