> In practice, maybe some roofer/plumber/landscaper forgot to do that and now you have a problem you didn't know you had

Seems to me like this should be the contractor's problem. If they did the job 2 weeks ago fine, but if they come along 6+ months later after the house is sold demanding payment from the new owner that seems ridiculous to me. Surely if these Liens are supposed to be public there needs to be a requirement that they are registered as soon as possible.

Otherwise it seems to me like this is a ripe opportunity for scams. Buy house, have contractors refurbish it, sell it for a much higher value, then the contractors register their debts and now the new buyers or their insurance is on the hook for the refurbishment.