Commitment° reduces overhead
If you're keeping all options° open, you spend a lot of time picking between them on an ongoing basis. You're constantly re-evaluating: should I continue with the current one, or try to find another? Commitment° avoids that.
For example, in a monogamous Marriage you commit yourself sexually and romantically to a single person, and among other benefits, it allows you to avoid this whole category of efforts -- which takes a surprisingly large amount of brain power.