If you take a train to work five days a week and it's "on time" (not delayed by 6 minutes or more) 85% of the time, you'll be late on at least one day most weeks. Hardly very punctual.

Personally, I think they should just abandon timetables, run trains as fast as they can, and if you need to be somewhere by a certain time, you give the planner a target reliability and it uses a probabilistic model of the entire system to tell you when to leave so you can arrive on time (0 minutes delay, or earlier) with that given probability.