I have talked to some landlords/landladies who are not keen to host or encourage folk sessions in their pubs and clubs.
The reason they give is that they have tried it in the past but sold very little beer/lager etc. Musician sessions,they say, are the worst culprits as they play and play all night and nurse half a pint for two hours or more.
Singers sessions,it seems, have fared better because they seem to attract more hearty (and heavy) drinkers but if they don't attract and actively encourage a sizeable (drinking) audience then it's a commercial numbers game again and landlords can pull the plug because of poor profit margins.
Unfortunately that's business and it is a sign of our times.

If you can find a great venue with seperate and distinct rooms, a friendly and supportive landlord AND locals, no juke box or TV, great real ale and a regular shedule for weekly/monthly sessions -
HANG ON TO IT WITH YOUR LIFE !!