Well for some it helps.

Not everyone has the "discipline" to take from the minds eye and put it into 3D space.
You state that for yourself its easier to go to Poser, tweak,  and then tweak the 2D image later.
Some "play" until (for them) they hit upon something that resonates with them.
Others need to "map" out what they want to do in 2D then goto 3D.

I dont think it hurts and builds another skillset. Also it may be necessary for documentation purposes in some cases.

"Few are agreeable in conversation, because each thinks more of what he intends to say than that of what others are saying, and listens no more when he himself has a chance to speak." - Francois de la Rochefoucauld

Intel Core i7 920, 24GB RAM, GeForce GTX 1050 4GB video, 6TB HDD space
Poser 12: Inches (Poser(PC) user since 1 and the floppies/manual to prove it!)