I might be the last guy who still misses knickers. Many sports have striped shirts and a few have ball caps. Knickers were the one thing that was unique, that instantly distinguished us football officials from any other sport's.
I also just think the tight socks looked a little niftier. Many baseball fans agree: It's a shame nobody in MLB wears stirrups any more. They just let loose pants hang below their ankles. Now we football officials are doing the same kind of thing. The more we look like we're wearing warmup pants, the less official we look, I gotta say.
I also hate having to spend an extra $10-15 to get each pair of black pants hemmed.
No argument on the comfort, though! Or the colorfastness.