I don't understand the constant attempts to paint places as "rugby cities'.
In domestic rugby, both League and Union attendances are beaten by football attendances, usually comfortably so, in every city that has a professional rugby team and a league football team, barring Exeter and Salford.
With Salford, that won't be because rugby is more popular but because most of the people living there support Man United.
With Wigan, it's only the Wigan - St Helens matches that attract attendances above that of the football team, and that's the town that people most often use an example of being more interested in rugby and they've not had any proper success since they won the FA Cup.
Plenty of the attendees will also be watching both.
If Bristol City were in any way successful, they would comfortably sell-out, but they've not been in the top flight for 43 years and their only achievements in that time have been promotion from the third tier and the Diddy Cup (where they took 41k to Wembley).