There's a multitude of well built riflescopes on the market, but one important factor for some muzzle loading hunters is the amount of eye relief that a scope offers.
Muzzle loaders can be somewhat different than center fire rifles in that they can recoil more so the shooter wants to avoid scope eye.
Another factor is that in many states BP deer season can take place in the winter when heavy clothing is worn which can affect the amount of eye relief needed.
So a scope with a 3.3 inch eye relief may not be as desirable as one that has 3.75 - 4 inches of eye relief.
Every hunter and every rifle has a different eye relief requirement based on their build, the length of pull of the rifle, the clothing being worn, the overall length of the scope and the amount of fore and aft scope adjustment that the scope mounts allow.
I think that's why dedicated muzzle loading scopes offer slightly longer eye relief than regular rifle scopes. But the hunting seasons and climate are different everywhere, and people do have their own preferences for their ideal BP riflescope.
The bottom line is that some of the better built riflescopes may not always be the best choice to mount on their muzzle loader.