Demos have been on the way out for a while. Studios get bigger, projects become more complex and deadlines get shorter. Cutting the demo out makes sense if it helps them get more of the actual game completed before it ships. Valve and Blizzard are in a unique position in that they've made their names synonymous with extended deadlines and quality games, I presume the only reason StarCraft II has a beta release was because it has such huge shoes to fill and Blizzard really has to get it right, as did HoN and LoL.
Wouldn't really bother me though, I haven't installed a demo in years. I think MechWarrior 4 was the last one I played and I had every intention of buying the retail version anyway. From a combination of publisher
PR spiel, reading a variety of reviews and waiting for a good price I tend to get all the games I'd like to play at a price I'd like pay. It's a lot easier to look for reviews and deals now with the internet, pre-net all you had were magazines and demo disks.