Why would my ex-mom in law have me as a named driver on her policy?

Been investigating why my auto insurance rates are high, so ordered Verisk Aplus report and Coverage Verifier. Turns out I was on my mother in law’s auto policy for 10 years?!? And 4 of those years are AFTER my divorce. WHAT. Like…there are amicable divorces, and mine was NOT one of those. I didn’t see or speak to my ex-MIL again, and if anyone had offered me to the keys to her car I’d have assumed it was a booby trap rigged (poorly) with explosives and run the fuck away. There was 0.0% chance I was going to ever be behind the wheel of her sensible sedan again, everyone in that family knew that, and yet…she kept me on her policy for 4 years? She’s a real estate agent and shrewd financially, so this was not an oversight. She’s also entitled and not above committing frauds. Having me on her insurance had to have benefitted her (or her family) in some way. But…What value could I be to her auto policy? Like, is a good driving record an asset, lol? Any ideas? I’m open to creative suggestions, lol.

I guess I should ask if there’s any way this could be influencing my rates today…the policy was cancelled 5 years ago. But I’m more interested in the possibilities of WHY out of personal curiosity. Like she couldn’t get rid of her shitty son in law fast enough.

Relevant details: in California. I have a clean driving record and a long driving history. I don’t know her driving record. She was like 75-80 years old at time. I would assume my ex wife was also on the policy bc it’d be even weirder if she wasn’t. Her son is a walking DUI, got 2-3 in those 10 years I was on the policy, and I don’t know if he was on his mom’s policy, but…if there was a way to spread his risk out, she would’ve done that, whether it was fraud or illegal or anything. Any ideas? Any warnings? Should I be concerned about anything?