'Technical reasons' is often given as an excuse for cancellation or delay covering everything from faults to lack of crew. What I'm saying is in all these cases 'faults' were mentioned. I don't really trust excuses given by transport businesses of any kind, unless I can verify them - but coming back to my question about the Dash 8s - I have seen several being worked on, I assume because of the aforementioned faults.
I wouldn't want to engage in speculation about other more commercial reasons for cancelling flights, though like many others, I've heard the rumours.