Because the buyer may not discover a problem - until he’s the seller.
This is yet another reason why nobody should buy or sell real estate without having an attorney. All of the documents are written by lawyers, and the bank’s lawyer is present at the close, most “homebuyers” go in naked and haven’t a clue what half of it means, and mistaken about the other half.
“Title insurance” protects the lender, not the buyer. They make the buyer pay for it (along with everything else).
I wouldn’t use an attorney except in NY. Attorneys do lousy title chains and their work frequently ends up in court.
Title companies do a great job.