Howdy,
I think that cost and availability are the most important factors.
Two points to consider:
The Remington is generally accepted as a stronger, superior design to the Colt. But the Colt was better marketed, more widely available and somewhat less expensive. Also the Colt was cheaper when sold to the Army, resulting in a wide distribution.
The Ruger is a fine gun for CAS, even more so because of it's durability under the stress of rapid firing. But shooters from the cowboy age did not shoot much, they carried mostly and used them rarely, so again, cost becomes the main factor.
Good question.. Adios,