I hate not having one on a backhoe. The extra weight helps balance the machine, and makes unloading off a trailer with a breaker on it not so tipsy.
I've ran skids of all types out here, and not one has had a 4 in 1. Quite honestly, when doing concrete demo, I HATED the skid because it didn't have a 4 in 1. Now in AC, we move more material without it, but ac is a specific animal.
I believe the reason for no 4 in 1 here is the amount of labor. We dont send an operator without a labor. It's rare. I've seen one with a 4 in one. It was a lone operator loading a pile of trash out of a warehouse.
The reason that matters is..... stupid.... and old. Supervisors and owners dont like seeing idle workers. Even if they have a traffic control paddle.
Imo, loading with a 4 in 1 is faster. You dont move the pile. You make less mess. You clean up better.
My guess is price is the biggest deterrent. 72" 4 in 1 is $2000-3000 more than a solid bucket. The other being, most skid steer operators aren't good operators. "That's why they are in a skid steer" would be the normal prejudice.