Dreamer... it boils down to diminishing returns. Those posted examples of drumming and percussion at the BFD or Superior Drummer sites, to my ears at least, sound EXACTLY like audio drumming.

Which they ARE..!

Don't confuse a MIDI kit with a robotic performance. Nowadays, most of the better style creators are using MIDI kits and real drummers to lay down the groove. And MIDI percussion is played by REAL percussionists. Combine the performance with a kit that, OK, there's aren't 50 different snare drum samples, but even 8 or so can fool the ear, and you have something much better than we currently have. Remember, drum samples are VERY, very short (other than cymbals!), so take up very little ROM compared to say a sax. I dare say, were the ROM for an SA2 sax sound tasked to doing a percussion kit, you could have many layers for each sound in the same room.

The combination of great samples with a great performance easily equals audio loops, but with none of the drawbacks.

That's a win/win, in my book at least.