Whilst we as pilots & cabin crew cannot plan to go into discretion, rostering and Ops rely on us doing it to get the schedule flown.
There are several notorious lines of flying with 4 or 5 short and 'long' sectors that are planned to go within 30 mins of max duty. We are all aware of easyjets on time performance problems particularly in the second half of the day, yet crews still go into discretion and so these lines of flying still get given.
If we stop doing discretion (even when it suits us) the company would have to address the issue eventually.