query: when did title insurance become mandatory

First, you must ask the question, who or what is mandating title insurance? It's probably the mortgage lender who is mandating a loan policy. The lender may be following their own standards or they may be following agency standards. Agency - FNMA, FHLMC & GNMA - standards set a bar for quality. Loans that meet agency standards are more easily sold in the secondary mortgage market, either through securitization or whole loan sales.

I've been engaged in agency standard mortgage lending since 1978. I can tell you we were originating FHA and VA transactions destined for GNMA pools. These transactions all had title insurance loan policies. So, getting back to your question, I don't know when the agencies adopted title insurance as a standard, but I can tell you that GNMA apparently had this standard by 1978.