And so self defence training reflects the life and death nature of a street fight more accurately?
You can use the tools learned in MMA. in dark corners, against ambushes and even against malicious people. (we have seen that every single post I have made) You can even add to those tools with other skills from outside MMA. But you need those basic tools first. There are very few illegal moves that cannot be trained using legal ones. Now this is important because the effectiveness of any move relyes on the individuals ability to apply it.
Competition places importance on the result of the training which you will struggle to get otherwise. You cant really learn to win if there is no cost to loosing. You also can't send people off into street fights as it defeats the purpose of self defence. So you get limited things you can do in a training setting.
Your mindset has to last the whole fight. For most people it does not go much past the first punch. MMA and sport in general use the method of pressure testing the person and the system to develop this. To do that you need rules because too much risk is detremental to creating a stronger willed person. You can't train effectively without rules.
If you can incapacitate a person using pads, using rules, and without malice. You will be better equiped to incapacitate someone when you dont use rules.