Well... that is at their discretion. It is their game. And I guess that's the price to pay for attempting to extend the longevity of ts4 long past previous iterations and long past where it makes sense... in my humble opinion.
Even though ts4 is 5 years old now, I know that I have to update my rig every few years if I want play any decent games that I'm interested in playing. Personally, I would prefer to be considering updating my systems for ts5 by this point in time.