From Anthropic's perspective, everyone pays to be in bins with a given max.
And to everyone's benefit, there is a wide distribution of actual use. Most people pay for the convenience of knowing they have a max if they need it, not so they always use it.
So Anthropic does something nice, and drops the price for everyone. They kick back some of the (actual/potential) savings to their customers.
But if everyone automates the use of all their tokens Anthropic must either raise prices for everyone (which is terribly unfair for most users, who are not banging the ceiling every single time), or separate the continuous ceiling thumpers into another bin.
That's economics. Service/cost assumptions change, something has to give.
And of the two choices, they chose the one that is fair to everyone. As apposed to the one that is unfair (in different directions) to everyone.