> in democracies you can reject the government

No, you cannot. You can reject the current party, but the government is much more than that. In the US, for example, the government is a set of institutions that were put in power in the American revolution. If you try to reject this your own life is at risk.

I would argue that many people do “reject” the government, but they do so by abstaining from the political process. This is why participation is low. It’s not a direct threat to the government so the government doesn’t do anything.

The U.S. government is confident enough in their appearance of legitimacy that they allow pretty broad liberty to criticize it. This is in contrast to other governments like China or Russia or even Singapore which are much less secure about their legitimacy.