I participated in a study where my EEG was taken while I watched some random videos, and half the time was spent on putting enough conductive gel in my hair below the sensors to get a stable signal, and afterwards I had to shower to get rid of the stuff.

There was a bald guy in the study who amazed everyone when he could just put on the cap to get a signal, so EEG might work as brain-computer interface for some people. But for the general population, it's just too much of a hassle.