It's the kind of business that mops up empty commercial space, usually on a "until we find a better tenant" serial short-term rental agreement. See also kiosks, nail salons, vape shops, "outlets", pop-up shops etc.

In many US metro areas, these are the first types of tenants who move into small strip shopping centers along secondary roads running through smaller suburban towns and cities.

I'm in NE Atlanta metro; it seems that you can't pass a traffic light without seeing a nail salon, a gas station, a cell phone store, and Subway. And these have been there for years right from the building of the building.

Perhaps the work required to convert a vacancy into/out of a dojo or similar is relatively simple? Sure you might need to put in a pair of locker rooms and/or and perhaps an office, but it's mostly empty space. Would something like that generally even have showers/plumbing needs?

Because a dojo needs lots of space. If it's not an elite dojo it means the prices for commercial space have crashed in this location.