providing a reason for your instructions doesn't hurt anything

I tend to agree in most cases. However, not all instruction-givers have good reasons for their orders. If they must provide such reasons before they are obeyed, and only inconsistently have them, that means that a plausible motive for their subordinates to question them is the desire not to follow the instruction. (i.e. subordinate thinks there might be no good reason, feels compelled to obey only if there is one, and is checking.) The motive associated in this way with asking for reasons is therefore considered harmful by the instruction-giver.

When I was a kid and got an unobjectionable but confusing order, I usually agreed first and then asked questions, sometimes while in the process of obeying. This tended to work better than standing there asking "Why?" and behaving like I wanted the world to come to a halt until I had my questions answered. Objectionable orders I treated differently, but I was aware when I challenged them that I was setting myself up for a power struggle.