Apple supported PowerPC Macs for nearly 20 years before switching to Intel CPU's
From System 7 all the way to OS X 10.5 Leopard.
So, what is YOUR POINT?
Supporting Windows XP for 13 years was Microsoft's choice and a very poor choice at that!
Trying to design/make newer hardware/software apps and security apps compatible with a 13 year old computer operating system to Microsoft's own detriment.
The original Mac OS design and all its forward incarnations up until 2000 was getting clumsy and kludgy.
Apple didn't want to keep back pedalling with keeping support for older Mac operating systems.
When SJ came back to Apple, OS X gave the Mac OS a new start with the Unix Mach kernel with an a complete redesign and refresh from the ground up!
This has always been what Apple does!
Apple has always placed limits on how long a Mac OS will stay supported on legacy hardware.
This is nothing new here, for long-term Mac/Apple users!
As far as Snow Leopard is concerned, it is still needed to get users access to the Mac App Store and for users still needing Snow Leopard for install discs for older supported Macs or those with missing SL discs.
Apple, also still sells OS X 10.7 Lion for those Mac users whose Macs can, at least, move up/upgrade to one more OS X level.
Apple, also still sells OS X 10.8.5 Mountain Lion to those users who still need a more current OS X version, but still need an older OS X version for older, legacy software.
Typically, Apple only supports a Mac OS for 5-6 years! Tops!!
Apple is 6 OS generations past OS X Snow Leopard.
At some point OS X Snow Leopard maybe still fine for application use, but will be of seriously limited use for online activities.
It's the way it is.
BTW,
I have been using both OS X 10.8 and 10.9 and fine them perfectly stable with most of my legacy software.
The only apps I have problems with on OS X 10.9.5 is my older iMovie '06 HD and Final Cut Express.
These two apps do work perfectly fine on OS X 10.8.5 Mountain Lion.