Unfortunately this has been a problem with Apple OS for a while now, only supporting the current the current 2 OS's (released every 1.5 years!). They have your money, time to move on to the next victim (er, customer)...

It's almost like it is assumed that if you can afford to purchase a mac in the first place that you don't mind spending that money to replace perfectly usable computer every 3 years.

Do I want apple to give me new features in that old OS? Of course not. But security fixes? Absolutely! Because those "outdated" computers ARE going to get used, so not only are they hurting their user base that would like to continue using Apple computers but is being forced into this situation, but these insecure computers also hurt everyone because they make it easier for the bad people to attack others with their bot armys made easier with no updates like these.