I used one
I used a chase on mine for all the reasons previously mentioned. I was lucky, my chase pilot is ex-military, built his RV-4, and is very good at formation.
One thing that hasn't been mentioned that may be unique to me was the comfort factor. Even though we were in separate airplanes, it settled my nerves a bit to have someone else with me - maybe 'human factors'?
And I think I would have been more disciplined in an emergency with someone watching - less likely to go for a hail mary.
I also agree that having a chase does not fit every circumstance.