It costs money
TO lay on extra ancillary services costs money. If people are not coming in as it is, then how will they make money?
Chances are, those who do go in are not local people. They are still likely to pay a nominal fee to enter, so there will little difference in attendances.
BAMBOOZLER remain a free service, not something that is only going to be available to those who can pay. I know its been revamped, but local museums are never going to be major attractions that people expect to pay for. Charging for entry will put them in competition with other attractions. Visitor numbers will plummet if you have to pay to enter.
I agree with Mavis Enderby, you can generate income in various ways but to make it compulsory to pay to enter will just cut off the service to those struggling to make ends meet in these difficult times.