They can't function without it, so the list does exist. The IRS keeps records of residents and their marital state (a required piece of information on the form).

But those records aren't really fit for the purpose of certifying that someone is not currently married, because (a) they do not include people who don't need to file taxes; and (b) they are only updated once a year.

For pretty much every other administrative purpose, it doesn't matter whether you're married or not, so I don't really see why you'd want the tax records updated more often.