Mostly, I wanted skirmishers that could go fast enough to chase down supply wagons. I (at the time) didn't know how to change unit skill to mod speed, so just wanted skirmishers that could get up on horses and chase things. The intention was to just use them as regular marksmen, who occasionally mounted up to chase things down. Mounted, the very long reload rate of the hunting rifles makes them horrid as skimisher cavalry, but I never intended to shoot as cavalry, so didn't care much.
They probably wouldn't be workable as marksmen with more limited availabiliy rifles, as they tend to take 5-10% casualties when I use them. The apparent lack of auto retreating, and their great vulnerability to fire when mounted means that I couldn't keep them supplied with whitworths or whitworth (TS). And the near invulnerability of cannons to melee means they aren't great at charging the guns, either. You can get them into melee with cannons easily enough, but the cavalry will often become exhausted while trying to melee the cannons. If the guns have already take a lot of losses from counter-battery fire, then the cavalry can be used to shatter them. And I don't think the ability to capture a few thousand dollars in supply of many missions makes up for their increased cost, increased casualties, and stamina loss.