I've found that whenever no preboarding of elites happens, it's almost always due to 2 reasons. First, the agents are doing a quick-turn of the airplane and are trying to get it back out ASAP. Secondly, there are so many Gold, Plat, Ex Plat members that 1/2 or more of the passengers qualify for preboarding and it does make for slower boarding. It's understandable once in a while, but not when it continually happens.

One more point, I'd like to see preboarding of the passengers in the bulkhead row as they are last on and the bins are usually full by the time they board. This holds up the agents from closing the door due to finding room for their bags.