Freedom of choice, plus the fact that Loads like the .44 Magnum are much cheaper and reloadable. Shotgun Sabots are neither cheaper or reloadable. You can buy a box of 50 .44 Magnum shells for about $28, while shotgun sabot loads run anywhere from $10 to $15 per 5-shells, depending on brand. M/L ammo is the most reasonably priced but not everyone is into hunting with a M/L. However if you feel you can do with a shotgun firing either expensive sabots or inaccurate 5" @ 75 yard Foster Slugs, then that is your choice.