The only problem with this is that it works in reverse. We could put people who haven't commited a crime in jail on the grounds that they are likely to or it helps society when their in jail.

Once you factor in the dangers of giving humans that sort of power, I think that "problem" goes away for the most part.

I think a lot of you are missing that (a version of) this is already happening, and the connotations of the words "jail" and "imprison" may be misleading you.

Typically, jail is a place that sucks to be in. But would your opinion change if someone were preventatively "imprisoned" in a place that's actually nice to live in, with great amenities, like a gated community? What if the gated community were, say, the size of a country?

And there, you see the similarity. Everybody is, in a relevant sense, "imprisoned" in their own country (or international union, etc.). To go to another country, you typically must be vetted for whether you would be dangerous to the others, and if you're regarded as a danger, you're left in your own country. With respect to the rest of the world, then, you have been preventatively imprisoned in your own country, on the possibility (until proven otherwise) that you will not be a danger to the rest of the world.

(A common reason given for this general restriction on immigration. though not stated in these terms, is that fully-open borders would induce a memetic overload on the good countries, destroying that that makes them worthy targets of immigration. So indeed, a utilitarian justification is given for such preventative imprisonment.)

Again, the problem is recognizing what counts as a "prison" and what connotations you attach to the term.