I'm sorry to say that, but in my opinion, a typical pilot will never understand the meaning and sense behind a CTOT. For them it's just a penalty, a cruel way for a nasty ATCo to humiliate them. I'm pretty sure it's because pilots usually don't have any knowledge of ATC. They rarely visit ATC facilities, they have little interest in our job. They don't receive much information about ATC during their training. These are the reasons that during flight, they are not aware of the fact, that there is a complex situation around them, where some conflicting decisions have to be made - for them it's only their aircraft, some other 'intruders' around them (of course it's obvious that these aircraft should have lower priority) and a stupid ATCo which i.e. gives them vectors for a too long final. I always wonder - how is it possible, that pilots are unable to understand, that next time it's THEM who will be waiting at the holding point and thinking 'why this damned ATC doesn't make more spacing to let us depart?!?!?!?!'
Dear colleagues from the other side of the mic, please understand this: a TWR ATCo usually (95%) has nothing to do with the slot. Slots are due to weather, due to ACC staffing shortages etc. TWR ATCo must enforce the slot. It's one of his major duties. Personally, I think that sticking to the exact slot time is a bad idea, it doesn't help anything - aircraft may gain or loose some airtime due to wind, shortcuts etc. - it's quite heuristic. But yes, in theory aircraft shall depart on the exact CTOT time, that's how we are trained, and yes, there are some employers that check it on a regular basis and punish ATCos if they don't comply with the exact CTOT.