Many pubs have become reluctant to promote musical evenings because there is far more money to be made in providing food. The margins on drink are slender, even on soft drinks, whereas food can be very profitable. Thus a back room or a snug bar that would once have hosted a session is now filled with tables because it generates more income for the licensee.
One also has to accept the fact that not everyone likes folk music. I've known a couple of sessions where the landlord was willing but the regulars objected and the sessions were stopped as a result. With the best will in the world, a musician who has driven 10 miles to get there once a week will drink less than a local who walks to the pub every night.