Great article on Brickset right now about "Whatever happened to baseplates?":
http://brickset.com/article/19387/whatever-happened-to-baseplates
This has been bothering me for a while, as I keep seeing set after set being released which would have benefited enormously from having a baseplate (or multiple). Not only do they tie the elements of a set together, but the raised plates could be used to make a much more impressive structure out of a smaller parts count.
LEGO knows this too, which is why they use box art to simulate the baseplate effect, without having to actually include one. Just look at the "Fun in the Park" set above as an example, or the upcoming Service Station. Now take a look at other recent sets that would have benefitted from having a baseplate (the Arctic/deep sea/volcano city subthemes for example), and imagine how much better they could have been. Furthermore, go through some older sets on Brickset that had baseplates, and now imagine if that baseplate had been removed - it sure diminishes a lot of sets.
LEGO has its reasons, one of which im sure is maximizing profit, but I've been hoping that they reverse their current policy, and we see the return of the baseplate.