I would think the main reason is probably the cost of insurance needed to cover the shop of possible safety issues or possible injuries. We all know that archery is very, very safe if done properly but that doesn't change the fact that accidents can happen and if they do there is the possibility of legal action against the shop owner. This can be covered by liability waivers but I would still believe that some major insurance coverage would still be needed as a back up. I think I remember reading somewhere that at the ATA show, that any manufacturer that was to have a shooting range at their booth needed a minimum of $1 million insurance.

Exhibitors who lease shooting lanes are required to provide
a proof of liability insurance in an amount not less than one
million dollars ($1,000,000) and said policy must list the Archery
Trade Association and the convention facility as additional insurers.

I would be willing to bet that most private archery shop owners would not want to invest in a long term insurance policy of this magnitude.