Mario, for instance, once you jump, there's not much to do until he actually lands

Mario games let you change momentum while jumping, to compensate for the lack of fine control on your initial speed. This actually does matter a lot in speed runs. For example, Mario 64 speedruns rely heavily on a super fast backwards long jump that starts with switching directions in the air.

A speed run of real life wouldn't start with you eating lunch really fast, it would start with you sprinting to a computer.