That is a good question and I have noticed the same thing as you. That might mean the "bug" life has become smaller or maybe other fly fishermen have convinced others to downsize their flies. It could be a little of both. For me, I still use sizes 8, 10, 12 and 16 for all my trout fishing and do very well. When I decide to use a dry fly, which is very seldom, a size 12 is the smallest I will use and it produces for me. I usually stick with what works for me and my "style" of fly fishing and disregard what others or books tell me. As long as I am enjoying my fly fishing and it is producing results, I will stick with the sizes that I have confidence in.