Great responses, but a little out of context... but then again I never provided the context!

Sorry about the snippet!
I fully agree that the switch cast is the basis for all casts. In fact, in my own learning curve the switch cast is far and away my best cast. Yet I would never fish with a switch cast! Per my comment above were it not for the switch cast, a critical learning tool would be missing and perhaps the bulk of the entire casting population would be affected (e.g.: "most would have given up long ago").
Allow me to clarify: living where I do and practicing as much as I do (virtually every day) I do a ton of switch casting to reinforce those elements as have been pointed out here. Finding a spot between trees on a frog pond or a boat launch to practice tends to limit one's options.
I am no expert but can form a good d-loop with consistency and know when to stroke forward to put what the loop has to give into the blank to load the forward punch. At this point, building muscle memory for a d-loop to cast without a directional change is no longer relevant except for testing a new rod, line or theory.
In essence, you'd have to agree that forming the d-loop for a switch cast and forming it for a 45+ directional change is dramatically different in terms of what the body, arms, and mind must do - I would go as far as to profess that this familiarity with straight-away casting is what makes directional change the hardest cast to master. Yet it's most similar sibling, the switch, is the easiest to master.
Yesterday, I stopped practicing with the switch. Today, I only used it to straighten out a line before a single spey when the sinktip fell too deep into the backeddy, etc.
Once again thanks for the advice. If I succeeded in explaining myself, do you think that practicing switch casting helps, hurts or neither?