Your shock is misplaced, since this issue is rampant on both platforms. Shitty software developers will do anything sleazy to make a quick buck.
I noticed that all of the spam I encountered was from games that had their own in-game currency. After the <blah>ing-With-Friends / Draw Something fads died out and I removed those Zynga games, I can't remember the last time I saw a garbage notification.
If I remember correctly, the pushback was before the new notification tray, so it may have been Android's own response to the problem.
But other than one Zynga game, I never, ever get spam notifications and that Zynga game was installed for about an hour or two.
Settings -> Apps -> Draw Something -> uncheck "Show notifications"
Screenshot: http://www.cultofandroid.com/16833/jelly-bean-tip-disable-an...