5% profit margin doesn't mean I will lose 5% on average. My risk will be pooled with reckless people and scammers. I know I am neither but my insurance company doesn't.

Then there are the sales and administration costs that need to be paid. On both their side (coming out of my premium) and on my side (coming out of my free time). I don't like keeping receipts and I don't like filing claim.

All in all I'd lose much more than 5%.