A Trainer also gives the basic of how things work.
It is a learning tool use in many aspect other then flight itself.
Understanding woodwork, mechanical, electronic and lift
also depends on the indiviual.

A simple question of , would every new beginner seal the hinge line,
or balance the wing ?
There's still people flying without stripes on the bottom of the wing on trainners,
if you know what I mean.

Flying is onething, repairs are another.
From my own experience, repairing a trainer or somthing like a 4*
is so much easier than an Extra or a Cap.