I don't buy it. The most common theft experienced by people is having their CC or debit card stolen and used by someone. Correcting that (and getting your money back/the charges reversed) is a simple and free process.
The more concerning problem is having accounts opened in your name. These can take longer to resolve, but generally you can file a police report and have the account removed closed/removed from your credit report for free. You can discover these accounts yourself by monitoring your credit report for free. You get one from each agency every year for free, so you could be checking every 4 months from just that. Many banks etc also offer free credit monitoring.
What you get on top of that from paying for ID theft insurance is effectively just reimbursement of costs to do the above, if any.
A GAO report said most only cover “covered postage and notary fees; the cost of obtaining credit reports or implementing credit freezes; costs related to replacing documents such as driver’s licenses and passports".
So, not much if anything. If you're really worried about identity theft, freeze your credit with each of the agencies. It may be free or cost a small amount depending on where you live.
I really can't see an upside to paying for identify theft insurance for 99.99% of people.