Exactly, the MBP is a performance computer, so it wouldn't make sense for it to have a slow 5400RPM hard drive while the MBA (cheapest Mac laptop) has a super-fast SSD.
Of course if you can't rely on external HDD or NAS, SSD is pricy in large capacity, but that's always like that when there's a transition in technology: either you pay the price for the newest tech or you get cheap, slightly outdated tech. Apple usually cares more about redefining standards than offering the cheapest products if you look at their past moves. They simply won't offer what they see as "on its way out" and move to what really is the future.
Some people are mad because they don't offer a regular affordable tower desktop computer, don't support Flash on iOS, Blu-Ray on Macs, USB ports and filesystem on mobile devices, optical drive on Mac mini, Lion on DVD, just to name a few, but Apple simply are like that and I think it's a good thing for the most part.
Of course people will also be mad the day the MBP will finally drop its optical drive and hard drives completely (whenever that is) but Apple do what they think is good, not what consumers ask for. That's the whole philosophy behind Apple and largely what makes them what they are today.
Maybe it's just me, but I really can't see a redesign that should last another 4 years or so come with a hard drive. If they feel people aren't ready for SDDs yet, I think they will keep the current design. That's probably why they still haven't updated it since 2008. Apple's vision of the future moves faster than most consumers', but it can't go too fast either.
