I had difficulty keeping small brook trout on the line a few days ago. I was using a 6'6" #4 Cult Fiber rod. I have thought about this before and I think the fish are so light they offer little resistance and it is resistance that is needed to put the point of the hook into the fish! If you couple that with a light line and soft short rod it becomes more difficult to drive the hook home. The point hardly enters the fish. It wiggles and of it comes. If you strike hard you may send them flying out of the water! I have done that back a ways.

Find some 10" - 12" fish and it will be different until you come on to a fish 20"+ and then it becomes difficult again as they have teeth and hard bone; it is difficult to get a good hook up.
On one summer night I had a big brown in the 27" class rising at my feet. I could see his dorsal fish as he rose which helped me figure the size of the fish. I put a light wire #12 dry fly on him. He took. I set and the the rod, a 7 1/2ft #5 Hardy Boo, bounced when I set and the hook came out. The fish continued to feed as if nothing happened! It moved up the pool in the dark and I lost sight of him.

It happens and it has happened to others I know most of the time you feel the tick, tick, tick of the hook on the teeth and that is it.
When we move to the extremes of fly gear you get what you deserve. Had I used a standard light weight dry fly hook instead of the supper light wire Orvis hook I would have had a better chance to sink the steel into him. Keep in mind the weight of the fly line helps set the hook or you have to set as a spinning guy sets or close to it. I was using a 14ft leader at the time and the fish was at my feet so the fly line was barely out the tip top. It was my own fault for that fish getting an undeserved pass.
Bobby