Because they're used for entirely different purposes.
"Unassigned work" is what queues are for. Customer Support Tickets, which can be divided into tiers 1 and 2 if desired (escalations). You bought some leads and now you have to go through them, nurture them, and ideally convert them. Normally, you take a case/lead/whatever from the queue, claim ownership, and the case/lead/whatever exits the queue. Depending on the sharing restrictions, it may or may not be accessible to your teammates... but it's usually "done" and taken care of. It's possible that if the support request is too difficult or you go on vacation, you'll have to return it to the queue. However, after it was taken out of the box, it dropped out of the line, making it invisible to the other guys.
Selling in a group is different. It's my chance to profit from it, and I intend to take advantage of it.