I do know where you are 'coming from' but surely a pub can be 'shared' - the informal music making can either be in a different pub, or can take place at different times to the (only slightly) more formal events.

There are church halls, town halls, arts centres, schools, marquees etc, where conventional festival performance is best suited and can take place without affecting informal pub sessions etc.

Pubs can be shared as you suggest but as so few people really understand the subtle differences between performance and social music making - the former is seen as more important and will always tend to take-over. Not because it is more important but because this is better understood, especially by organisers, licensees and other customers.

Some of my most frustrating festival experiences have been wandering about with lots of fellow musicians and singers who are more than willing to play, trying to find a pub where they can. When there was no shortage of pubs but all the suitable ones were already being used as venues for official festival performances. Or of having a really good informal pub gathering stopped or it nature altered to enable a scheduled performance to start.

There is room for all kinds of festival events I just think that wherever possible - organisers should try to ensure that one form is never prevented or inhibited to enable another. That enough suitable venues are found. And where these are limited and pubs are used for festival performances, that some are set aside to enable informal musical gatherings to take place.