I teach high school physics (Conceptual) and AP Physics (non-calculus).
And I do derivations in both. Very, very few in Conceptual and lots in
AP. I also give extra credit for those homework problems in the book
that require derivations (AP only). This is the reason.
1. Derivations show that important physical phenomenom can be discovered
by methods other than experimental. Relationships that were not obvious
"pop out" during derivations.
2. Derivations show part of the research process. The relationship says
"this should happen." Now lets go test it.
3. Derivations help develop a perceptual skill to which students are
almost never expose. It's almost a puzzle solving skill. And for some
wierd people (like me) it's fun to mess around with bits and pieces of
relationships and fit them together in a new way.
4. Derivations can show the interrelationship between phenomenon.
I suspect that many theoretical physicists may be good jigsaw puzzle
solvers.