Just an update...

I called Frontier and this is definitely their standing policy. It is very inconvenient to me. Like was previously said, this may be a way to discourage people from buying at the airport to save the CIC fee.

When I mentioned that one could buy online without showing a driver's license (obviously), the agent just reiterated that it was "to make sure the names match up" when buying at the airport. In other words, a non-answer.

I am hopeful Spirit does not start a similar policy...