I dunno... I just feel like I notice the difference. Perhaps a slight difference in the bindings or something, or perhaps because the edges don't wear exactly the same, thus the right edge of the right ski may be duller than the right edge of the left ski after a while, and as the skis wear down that way, I become accustomed to it? Just a guess, but I notice.
I haven't skiied at all this year... I usually put the left ski on first. After I toss them on the ground, I know that sometimes I'll step into the one of the left, and sometimes the one on the right, then lift the left foot with the ski and place it on the left as I insert my right foot. But, for the life of me, I can't remember how I recognize which was which. (*was* because I'm going to buy new skis... I shattered the plastic in the back of both of my boots last time I skiied. I always take the free lesson when I ski... I always get into the next to expert group (9th out of 10), and the instructor invariably thinks I can't ski since I had the old Elan unshaped skis from the early 80's, and racing boots! (worked fine for me, and I could never afford new equipment) Time to get some nice boots and nice shaped skis though!