Question for anglers

I've been a fisherman all my life, but there's one observation I've made that nobody seems to be able to answer, even fellow anglers. All anybody has ever been able to come up with is "I don't know. I guess I've always done it that way. Never really thought about it".

Here goes.

Right-handed people cast their line and hold their pole with their right hand, lefties with their left hand. When trouting, right-handed people reel their line with their left hand (since their right hand is holding the pole, right?). Same scenario for lefties. Hold the pole with the left hand, reel the line with the right.

Here's my question:

When salmon fishing, why do people switch hands and reel with the same hand they normally hold the pole with? I guess I'm the exception to the rule, as I salmon fish the same way I fish for trout, but EVERY other salmon angler I have seen will switch hands when they play a fish, choosing to reel in their fish and hold the pole with opposite hands. Wouldn't it make more sense to have your strong arm hold the pole when playing a mighty atlantic salmon? Why switch hands?

This one has be dumbfounded, and like I said, even seasoned, veteran anlglers can't come up with a logical explanation.