Perhaps this isn't the same for everyone, but I personally find it a lot easier to run a particular time (near my PRs) for distance events when there are other people I can draft off at or near the pace.
I understand that this is most likely all mental. But if you were to try to explain this phenomenon to a disbelieving non-runner, what would you say?
Are there any studies that show a benefit? All I was able to come up with is that all of the WRs for distance events need rabbits. But I couldn't explain why they need them.