The main issue is that there's nothing at our end set up to fulfill recurring payments, no way for sellers to manage subscribers/memberships, no way to schedule different mailings or downloads or shipments on a periodic basis, and really nothing we have at present could add anything of value to what PayPal's Recurring Payments solution can already do as-is, either by itself or combined with existing solutions to manage email newsletters (e.g. Aweber) or memberships (e.g. FrontDeskApp).
Presumably sellers don't want to keep issuing every buyer the exact, same download and/or thank-you email on a periodic basis; just letting buyers set up a recurring payment plan is one thing, but those buyers would expect to get something for their periodic payments, and we just have no way to manage doing anything for those repeat payments. Sellers inquiring with us about recurring payments have described a pretty wide variety of completely unrelated things they want to do with recurring payments, so building a system to accommodate all of those possibilities would be a massive undertaking that would divert our Development resources away from other projects of benefit to all or most existing sellers using our system.
