Far from a pressing need to upgrade, Snow Leopard users - and users of any other version for that matter - can simply install Vmware Fusion and run games built for Windows in the virtual sandbox environment like I do; virtually no difference in quality in any respect and far simpler and cheaper. What benefits over and above the iOS eye-candy frills really come with 10.7 and 10.8, 10.9?
What pressing advantages came with Snow Leopard over Leopard, above some code reduction (namely removing PPC support) and the addition of some stuff that no one uses (i.e. OpenCL) ???
Seriously, your argument could apply to Leopard over Tiger for that matter. While there were some improvements like Spaces, they were pretty much candy-coated fluff while Leopard was considerably slower than Tiger (not a great trade-off, IMO).
The point is that if you're going to use "it works fine as it is" argument for every single upgrade in existence, you will NEVER EVER upgrade and instead just whine about being forced to upgrade at some point at which point the cycle will continue.
Don't get me wrong. I'm not one to want be be forced to upgrade either, but having finally upgraded from Snow Leopard to Mountain Lion on my Macbook Pro from 2008 after getting a new Mac Mini that already had it on it (which convinced me the upgrade wasn't going to be so horrible after all), I can say that other than losing Rosetta, there was no reason NOT to upgrade (other than a few bucks to do it). It runs just as well/stable as Snow Leopard did and my software is all at the same level again with my desktop.
As for Mountain Lion improvements, I have to say after using Mission Control, I actually vastly prefer it to Spaces since it's basically Spaces and Expose combined and therefore saves me bother since one mouse movement does both. On the newer computer (Mini), I can echo my desktop out to any AppleTV in the house (requires support of GPU; my MBP won't do it). File sharing is simpler with supported hardware as well with AirDrop. "Messages" support is far more useful than I imagined it would be. LaunchPad can even be useful (if organized into folders) to find categories of applications faster than the Apps folder like games, web cam utilities, etc. Yeah, you could organize actual folders like that if you wanted, but this doesn't disturb the main Applications folder at all. It's basically a lot of "fluff" that you don't "need" but some are nice improvements to the GUI (slow evolutionary ones rather than night and day). Otherwise, I hardly notice much difference in day-to-day operations at all. The one thing I DO notice is that software all seems to support Mountain Lion while that support is drying up for Snow Leopard. And THAT is the main reason I upgraded (e.g. if I want to run the latest "Logic" software, I need Mountain Lion whether I like it or not).