If you use an LMA and you want your patient to not move during surgery you need
a) a MAC+ of volatile, or
b) less than a MAC of volatile plus something else with a partial MAC equivalent (opiate, benzo, ketamine, etc) OR effective regional/local, or
c) paralytic
Most sane people don't use a pure volatile technique for either a LMA or ETT case. The point everyone else has been making in this thread is that (absent a regional technique providing a surgical level block) the depth of anesthesia required to tolerate the procedure is going to be sufficient to tolerate
either a LMA or ETT.
This notion that general anesthetics with ETTs somehow always (or even usually) require deeper levels of anesthesia is bizarre.
These are simple facts that everyone knows.
I agree with you, that beginners and unskilled people lean on paralytics as a crutch to get through inelegant / unbalanced anesthetics with ETTs. But IMO paralytics are way overused in general, and I think you're confusing
that problem to be related to the airway device chosen.
Avoiding excessive muscle relaxant and the cost/PONV associated with reversal is a good thing. It's possible to do that with an ETT,
especially in the sort of cases that can be reasonably done with LMAs.
To each his own (and again I like to use LMAs in
simple cases to keep them a little simpler) but dogmatically declaring that "ETT requires deeper anesthetic levels to maintain anesthesia and that leads to more PONV and longer PACU stays" is just wrong.