Using a crockpot as a humidifier is either a benefit or a hazard. If it's a benefit, it's not my problem.
The big advantage that a crock has over a purpose-built humidifier, such as an ultrasonic, is that the crock only releases the water and volatiles into the air. Minerals and other things that don't evaporate below the boiling point of water, remain in the crock (and have to be cleaned out, which will be much easier if you don't let it run completely dry).
A crock is less energy efficient than an ultrasonic, but since you're more likely to need it in winter, the excess heat is not wasted.
I generally prefer an ultrasonic, but it depends heavily on the water used. Our well produces liquid limestone. If we humidify with it using our ultrasonic, it coats everything with calcium carbonate. In addition to being a cleaning nuisance, I suspect this can actually result in failures of electronic devices around the home.
So, rock the crock.