Perhaps a reason for pilots querying these instructions is that there seems to be an increasing trend to descend a/c early due to standard handover procedures - nothing to do with traffic on the day. We are all flying around with the minimum fuel consistent with a safe operation, and having to start descent 50 or more miles earlier than expected takes a big slice out of fuel at a time when there's no opportunity to remedy the situation. Once one is familiar with the route it is possible to anticipate such early descents and plan accordingly. When we do get an early descent the majority of pilots will descend at the minimum rate of descent, in an effort to save as much fuel as possible, but probably negating the reason for being given the descent in the first place.
If ATC are going to operate these standard descent procedures, they should be published to the airlines. Pilots would then be expecting the early descent and could plan their fuel accordingly. If we make the effort to work together, misunderstandings can be avoided, and the ritual trading of insults could be reduced, although I suspect never avoided altogether.