What many people fail to realize is that being on dedicated tracks, C-Trains need to maintain their schedules up to the second. They are not like buses, which are already at the mercy of conditions of roads, which they share with other vehicles.
C-Trains are interdependent on each other at junctions and tracks at which they cross each other.
Stretching the 18-second door opening can become cumulative if drivers keep extending it to accommodate latecomers, who should have been there early, anyway.
This can cause a chain reaction delaying other trains. Moreover, passengers will come to expect this all the time if drivers do it even once, as is human nature.
I say C-Train drivers are doing a fabulous job by rigidly adhering to a zero-tolerance policy against latecomers. If they cannot pull up their socks, let latecomers wait for the next train patiently. Calgary Transit is not their babysitter.