When we had tracks in London, I regularly attended Wimbledon, Hackney and Crayford. You knew which night of the week they ran and didn't need to check the fixture list as they ran every week. Len Silver made a point of 'Make it a date, Friday at eight' and that is exactly what the fans did. The same weekly format was the norm throughout the country so it meant riders were on average racing one home and one away meeting every week during the season.
How the promotions get things back to that is a major problem to which I don't have any real answers. Back in the 60s and 70s supporters would arrive in equal numbers for league, KO Cup, local derby challenges and individual meetings. These days many are only interested in league matches and don't even support a second team in a lower league (Oxford being a notable exception).