I don't know that info for sure, but I'll risk hazarding a guess that it's to do with the fact that providing Railgun has a cost for CF. The CF servers need to

I don't know that info for sure, but I'll risk hazarding a guess that it's to do with the fact that providing Railgun has a cost for CF. The CF servers need to manage a separate chunk of memory for the customer cache and this is outside of the shared caches that can be used for assets. It also requires you to install something on your server (the vast majority of CF features don't require this), and that introduces additional support costs. Wherever there is a real cost to supply a service, you usually see those things in the more expensive plans. Where it's possible to offer something at negligible cost, you usually see those things in the cheaper plans. And yes, if something has virtually no cost to offer then it's a benefit to the security and performance of the web in general if we can push those things into the free plans and give them to everyone. There are exceptions to this of course, Universal SSL is an example of a feature that has a cost but the benefit to customers and the web in general is so significant that we give that on the free plans.