Like I said, this is a recent epiphany for me after being exposed to the concepts in more depth so I may be off-base, but from what I understand the Pareto Principle makes it clear that 80% of the income a game makes will come from 20% of the playerbase. And that then goes even further that 80% of THAT income comes from a further 20% of THAT, smaller, playerbase. Down to the point where you realize about 50% of
ALL game income comes from something like 0.15% of the total playerbase (that figure may be misremembered, but I'm fairly certain it's accurate.) If WoW did not have tokens and only had the subscription this would not be true, but because it does contain a method of throwing cash at the game to progress I can only imagine this principle is in effect. This is highlighted by the fact that as the playerbase dwindles, which we know it has, the games income seems to be holding steady or even, at times, increasing.
The only real purpose for the majority of non-whale subscribers is to provide content
FOR the whales
They need casuals to lord it over and beat in PvP and they need hardcores to carry them to their desired goals (be it gear, cosmetics, whatnot). But those players only count insomuch as they serve the whales needs and it's likely that the game could shed a not-insignificant number of them and still keep the whales happy and spending.
Again, I don't think this would be true of WoW were it not for the Token ... but ever since the token was introduced the game design has ever moved towards a system that benefits whale players, IMO.
This video is a good primer on the concept and very recent: