Why Shul is like a Gym

The other day I went to a meeting about alternative and itinerant minyans that been springing up here over the last few years.
Their hallmark is DIY enthusiasm and volunteerism.
In contrast, established synagogues maintain a professional infrastructure, financed by congregational dues.
As Rabbi Jeremy Gordon of the New London Synagogue observed, shuls are rather like a gym: 100 per cent of the members pay for them, maybe 20 per cent use it monthly and five per cent on a weekly basis…
But is that shul model going to be sustainable over the future?