I'm reading Morrison's Supergods, and he makes a pointed comment: the original origin of Spider-man took 11 pages, but Bendis needed six twenty-two page comics. I'd suggest that this isn't all Bendis's fault: readers demand a certain amount of decompression these days. Justice League arguably pushed it too far in their opening arc.
But DO readers demand the decompression? I do think that readers want more depth to the characters that used to be displayed, BUT, I don't know if they want the decompression. For me, honestly, when I read a trade, it doesn't feel decompressed there.
I think publishers are trying to write for both markets (the monthly and the trade) which works to various degrees of success.
It's probably a little bit of audience desire and a little bit of business practice that got us to where we are with the decompression.