One case is titles don’t transfer instantly. If there’s a backlog and something happens during then, insurance can help with that:

Beyond that getting a lawyer to handle a sale doesn’t seem much different with or without a realtor. They have their own liability insurance.

Realtors def help navigate the market agent they are competent in it.

Here's an example: I've got a house under contract and in the title report it shows that in 1906 (!!) the then owner of the land (prior to the house being built in 1946) signed away mineral and timber rights. Unclear at this point who those rights belong to, but doesn't appear to be the homeowner. In another case, I had a seller client who had been a victim of title fraud on a piece of scrub land. Title insurance is something you hope to never need, and admittedly it mostly involves family esoteric scenarios, but it really is there to protect buyer and seller in their ability to convey property.