How many journeys are really that time-sensitive? If they are, how often is it that you have a choice of airlines whose schedules are so close that punctuality becomes an issue.
Take for example a trip from the near Continent (AMS, PAR, BRU) to London for a 10:00 meeting. Because of the hour change you have to take a very early departure or go the night before and spend a fortune in a hotel. So punctuality is a major factor in your decision, but early morning arrivals into LHR can spend an age in the stack no matter which airline you're on. So punctuality league tables will tell you the relative performance of BA, BD, AF, SN, KL but when it comes to an 09:00 arrival at LHR they all have the same problem.
However, punctuality is a perceived measure of an airline's efficiency, and travellers probably rate it quite highly in their criteria for choosing a carrier even though if they stopped to think, two comparative figures on a page probably have very little to do with what they will actually experience, and whether it matters anyway. And in marketing, perception is everything.