Out on my usual Sunday run and i got to thinking (as you do), well when your cassette is worn beyond belief and the chain is jumping like a bitch because yours truly hasn't replaced the chain as often as he should so the middle sprockets are like shark's teeth.
So, i was wondering why doesn't anyone make a cassette where the middle sprockets are tougher than the low/high gears as the middle of the cassette is where most people spend most of their cycling. The largest/smallest sprockets could be slightly softer as they are only used for shorter periods of time when climbing/descending respectively (unless you're a cycling god and spend all your time on the 53/11 combo!).
Think of it like focal lengths for photography lenses - the 28/25 tooth sprockets being like a fisheye lense which gets used infrequently and the 12/11 tooth sprockets being like 300/400mm telephotos.
Mad idea or am i barking up the wrong tree.....