Because nobody wants the government to stop being the only one who is allowed to deploy violence. So the monopoly on violence is not in question.
The solution to the government abusing its monopoly on violence is accountability and regulation, not to remove the monopoly and allow people to just shoot each other freely.
I didn't bring up legitimacy, by the way, you were the one to claim that the government doesn't have enough support from the majority. That is an unrelated issue, as far as I'm concerned.