99% of oranges and greens become Forgotten Souls and it takes 50 of them to re-roll one normal orange or green you really do need but require the ancient.
There are still some insanely difficult items to obtain. Yang's Recurve, Wand of Woh, Band of Rue Chambers, Slanderer/Little Rogue just off the top of my head have given me great pains. Meanwhile how many people are running around in one of the 100's of Blackthorn's pieces they've had drop?
Diablo III is not a special snowflake game like World of Warcraft where someone with Warglaives either is extremely lucky or entirely too persistent. Do you really want to spend 10-60 weeks getting an item/set like that?
Diablo's end game is all about pushing paragons and GRift levels. I don't care if you're full ancient with 400 Caldessan's on every piece, you may still not be good enough to hit 100's.
If this game were all about gear and had zero skill I might agree with the principle of drop rates being too high. However playing a zDPS monk and needing health globe bonuses on top of vitality, life per hit, resistance and the like can I tell you how many Hellfire Amulets I've had to make to get on with a useful passive, 3 good stats, health globe bonuses AND ancient?
The line of good and great pieces is so big that merely having one doesn't equal its usefulness. We've all had items where the "normal" is better than the ancient. Drop rates reflect that fact.