Replying to self (too late to edit): One other reason it developed this way, I think, is because of the strong industry participation. Industry researchers ofte

Replying to self (too late to edit): One other reason it developed this way, I think, is because of the strong industry participation. Industry researchers often are willing to write a short conference paper: Usenix, SIGGRAPH, etc. But they usually (with exceptions) have little interest in writing up a 20-page journal article and going through a heavyweight revise-and-resubmit review process that might take a year. So the good industry research ends up mostly at conferences, and since some of the industry research is very high-profile (e.g. Pixar stuff at SIGGRAPH), it further cements the conferences' reputation as the place top research appears.