Not necessarily a lack of confidence, more likely a lack of awareness of the detailed ins and outs of how we actually do our jobs.

Additional alternatives might include (1) A particular aircraft swap indeed doesn't make sense to them (not having the "big picture" I mentioned earlier, or maybe due to a multi-aircraft swap); (2) Their statement is a simpler, quicker, and non-technical explanation of the situation (let's face it, they are busy up there); or (3) They are commiserating with you for the delay. Sometimes it's a combo platter of all three...

The bottom-line (for Customers and crews alike) is that when something like an unscheduled aircraft swap occurs, it's being done for a reason, and a good one, although that reason might not not be as readily discernible to crews or to local ops folks. Despite some assumptions to the contrary, all airline employees are not fully interchangeable in that each knows 100% of every other employees tasks and what goes into them. It'd be like going into a hospital and asking the first person one sees (say, an admissions clerk) a complicated question about a surgical procedure, or conversely, asking a surgeon about admissions paperwork and insurance hoops. We all have our specialties, and while we endeavor to explain the rationale for our decision making to others, there isn't always time to, since we usually have other pressing operational demands on our time, especially if some of the other usual culprits (bad weather, ATC delays) are giving us a busy day..

Cheers..