I understand the concern, but having more users or more interactions should be a greater benefit for the chain
Of course that is true. I imagine you will get more usage (perhaps a lot more), and at lower cost too, either way, certainly compared to no RC delegations at all. Needing to delegate or buy HP along with RC just to enable usage is a much higher cost.
The point I'm making here is that the biggest part of the savings comes from being able to delegate RC at all. There is some savings from pooling, because users can share delegated RC, but with sharing comes a higher usage factor, and higher costs, all else being equal. So the benefit from the latter will be muted, and also comes with the tradeoff of increased cost to users not part of a pool.
None of that is necessarily a bad tradeoff. As you say a lot of it comes down to enabling more usage, which is a good thing overall.