The competitive scene is probably also influenced from the speedrun community. And the speedrun community has really worked out the kinks in their ruleset, as in most games, you need to find the sweet-spot of allowing hacks and innovative techniques to break the game, but not too much that it becomes uninteresting.

For example, in Super Mario Brothers non-TAS runs, the rules are based around the controller and execution environment. You are not allowed to modify the controller or tilt the cartridge, but that's it.

Having the rules only limit the tools required, just like in sports, is quite elegant. If somebody figured a way to play faster with their teeth, it would be allowed, and rolling the controller is just something like that.

On the other hand, people found out that you can perform certain feats in SMB by pressing the left and right button at the same time. This is considered impossible with the standard D-Pad (without e.g. cutting it in the middle), so that is banned. At least until somebody figures out a way how to do it with the standard D-Pad.