You say that like the OS requires some large amount of RAM; the OS isn't demanding at all; yes they added a few features but for people with 2/4 gigs of RAM they won't see any slowdown or bogging of the system because of it.
They know there are a ton of MBs out there with only 2 gigs of RAM, they won't hinder the performance of those many machines.
I beg to differ. In Snow Leopard, I usually use up 2-3 GB with just regular use (Safari, iChat, Mail, iTunes, Calendar, maybe some Skype). In the Lion GM, it's not rare for me to have 5-6 GB used up with those open for no more than 2 hours. Lion definitely gobbles up RAM. That's not to say that it wouldn't be ok with 2 GB of RAM, but just the fact that it so easily actively takes advantage of so much RAM shows that 4 GB standard would be highly beneficial.