I use standby very frequently on my laptop, which I literally use on my lap quite often. And one reason I really like to see standby happen quickly is so that I know I can move the machine safely, without the chance of a disk head impacting a spinning platter.

So I wouldn't like the computer to automatically hibernate when I all I want is for it to suspend. As Scott says above, writing a couple of gig to disk takes a bit of time, and that's time when I can't be moving the laptop.