I think it might have something to do with claims.
I phoned up before I wrote off my car, and was told that they would insure alloys, after I wrote my car off, shock horror, they had changed their policy and you now had to be over 25 to modify.
I told them I was off to another company that was cheaper anyway.
Woman on the phone said, and I kid you not, "why not, if you can get it cheaper thats what Id do".
Lol, what a businesswoman, I bet direct Line lover her.