I'm no expert but you fail to do several important things when you don't raise when you should:
a) you get less value from the good hands/situations (as you know a butterfly chip preflop can bring about tornado raises on the river)
b) you let mediocre hands get a cheap shot at the pot
c) you don't thin the field so as to play against the "right" number of opponents for you in the situation.
d) the pot building process is deferred, thus leaving plenty implied odds on the flop. This may or may not be avoidable depending on stack sizes, but if your hand is good but volatile on the flop you don't want being limited in the amounts you can bet (relative to the stacks).

Position is of paramount importance in your decision to raise or not, and raising from early pos should not be frequent, but hardly ever raising from any pos is certainly sub-optimal as you said.

FRC