Actually this is quite incorrect and not always the case. The MacBook Pros from early 2011 can run Snow Leopard just fine, although macs that were released new as of July 20, 2011 or later, will generally not run Snow Leopard .
Even though the early 2011 MacBook Pro's shipped with Lion and all the function keys for Lion, they can run Snow Leopard and that's just the first anomaly I can think of off the top of my head. There are many interchangeable oddities in Macs released around that period with Snow Leopard.
I specifically bought my 2011 model MacBook Pro as its the most modern MacBook Pro that can run Rosetta which I need from time to time for old PPC apps. It will install Snow Leopard off a disc with the 10.6.6 update, it just wont install off a generic retail disc.
There are actually numerous people who rolled back to 10.6 because of the numerous bugs and performance issues it had early in its life cycle, just Google it. It's not just for the reason I said, but that's the reason that's applicable to me.
There is some software and particularly most Mac games prior to the release of Steam that are only PPC binaries and due to having third party developers like Aspyre most are unlikely to have updates with fat binary patches. Without Snow Leopard I couldn't run them.
Off the top my head, all Mac Pros that look like this can run Snow Leopard:
Mac minis with at least 1 GB of RAM and 4 and 5 USB ports on the rear as shown in the image below will run Snow Leopard, those with less than 4 USB ports will not run Snow Leopard.
All iMacs which look like this will run Snow Leopard:
- 10.6.1 10.6.2 Delta 10.6.2 Combo 10.6.3 v1.1 Delta and 10.6.3 v1.1 Combo 10.6.4 Combo, 10.6.4 Delta, 10.6.4 Mac Mini Mid 2010
- 10.6.5 Combo, 10.6.6 Delta, 10.6.6 Combo, 10.6.7 for early 2011 MacBook Pro.
- 10.6.7 Combo, 10.6.7 Delta, 10.6.7 font update to all previous updates 10.6.8 delta v1.1 (7/25/2011) and Combo v1.1 (7/25/2011), and the followup Thunderbolt update for 2011 iMacs and MacBook Pros for installation after 10.6.8
You will want to install 10.6.8 for ThunderBolt enabled Macs.