My comment was a little tongue-in-cheek, but you make a good a point. As other posts have mentioned, the email would be a proxy for other factors associated with age that age by itself can't capture.

If it's age at all. I'd bet it might be more closely associated with something harder to articulate or measure, along the lines of "a proclivity for clinging to subpar solutions." Someone who uses a subpar email service might also have ingrained poor driving habits.