FWIW, I've had those on my kite for most of a season and they still look like new (if you were concerned about rust) and there are no obvious sharp edges (if you were concerned about that). I think they are mainly not there by default due to cost. It is a ball bearing swivel with more parts that costs more to produce. I have seen these pulleys on some production kites, but I forget which brand.
The cover idea, while interesting, seems like more work than you need to do. Most people are trying to speed up the set-up/break-down process. Why make this take longer by putting little condoms on your pulleys? I hear the reason, just seems overcomplicated.
That said, the new Slingshot T3 comes with covers for the pulleys. Well, I think they are for the pulleys...they come covering the knot that connects the pulleys to the kite. So they could be there to protect the pulley from smacking against the LE, I really don't know. But, in one of the directions it says to slide over the pulley. Whatever the case, here are pictures of them covering the pulley and off one of the pulley uncovered when I was moving a line around;
Sorry to come down on the pulley condom idea. I just prefer low maintenance solutions. For me, replacing the pulleys was the choice over having to free them each time I rode or work on a way to shield them from the sand. All good ideas, though. That's what's great about the forum. Many different ways of looking at the same problem!