This is absolutely correct. Consider the following as an example to why a pure likelihood of recidivism system would be undesirable even from a utilitarian perspective:

If someone murders their spouse, and it's clear that they would never murder anyone who isn't their spouse, locking them up causes them to suffer and prevents no future crime. Indeed, it costs the state money in the form of their lost taxes and imprisonment costs. An injunction against ever marrying again would be the cheapest way to prevent them from committing another crime.

But if this were the punishment, how would that effect people's decisions to murder their spouses? Or commit other crimes they could prove were one-off events?