Simple. Nobody with any sound business acumen is going to invest money into building a new or reopening and old Speedway venue just to please a few hundred punters who can't let the past go.
Speedway needs to focus on what it has left now. The likes of Coventry, Swindon and Wolverhampton can argue all they like, but they are living in a fantasy world. They will NEVER reopen.
Speedway. Is. Not. Viable.