Because the free-priced government option will drive out the non-free commercial providers. Even if this only lasted a few years, it would put some of them out of business.

In other words, for the same reason we have laws against unfair competition.

The U.S. used to primarily have for-profit firefighting. Switching to a state-run system drove out the commercial providers. And that's by all accounts, a wonderful thing.

Business for the sake of business is not necessarily good. If the business does not provide real value any longer, it shouldn't exist.

So why not have the government run everything then?

Government for the sake of government is never good.

Who are you arguing against? I never suggested anything of the sort.

Some things lend themselves very well to for-profit businesses. Others do not. Firefighting and filing your taxes to the government strike me as two things the government can probably handle better than capitalists.