I disagree that it's the standard. Mahomes just signed a 10 year deal.
Permanently? I haven't seen anyone say that, where did you get that idea from?
OK, let me try to explain. We are not a super bowl contender at present. To get there, we need to fill some gaps. To fill those gaps, we need every resource available, including salary cap room. Signing Dak to a 4 year top dollar deal assures us that we will not be able to build the team. Make sense now?
Take Mahomes, for example. He signed a long term deal, which allowed them to sign Chris Jones. How? By having a lower salary cap hit the first 4-5 years.
Do you get it now?