I just had another thought. Though the only thing I know about MathWorks' subscription model is what has been revealed in this thread, it just occurred to me that allowing someone to continue using software that they once subscribed to has major pitfalls for the publisher. For instance, it wouldn't take long for people to figure out that they could game the system by subscribing for a single month, paying their $9.99, then canceling. They could then go on using two versions (both Ps and Lr) that they had just rented until such time that they wanted to "upgrade." They'd then resubscribe, get the newer versions, then cancel again. This tactic would cost Adobe millions.
Technically Mathworks and similar companies don't offer a subscription model, but rather a software maintenance service (SMS) model. They sell you a perpetual license to use the software for a sizable fee (similar to buying a new copy of PS or LR) that includes 1 year of free software maintenance, then prompt you to pay a much reduced fee (e.g. 20%) each year after that to renew your SMS. So it's like buying a full update every 5th year, but giving you all the updates in between and giving them a steady revenue stream. Lots of technical software I use works this way.
As said up the thread, the big benefit for users is that they can keep current on all the releases as long as they want, but stop paying at any time and just keep using their last version as long as their hardware supports it. They can restart their SMS later, but they effectively have to pay a catch-up fee equivalent to the time they skipped (or just buy a new full license with 1 year SMS if that's cheaper). So there's no way for the publisher to get screwed by people churning their subscription as you postulated.
Also, I'm not saying there are not people who benefit from the Adobe subscription model. As others have said, if you're a media professional who always has to stay up to date on versions, or if you're just starting out and haven't already bought these professional-grade software packages, it's a huge bargain. No doubt about that. It's those of us in between who have already invested in these tools and want a way to upgrade only if and when we really need to and have the means to, but want to have perpetual access to our catalogs and editing tools REGARDLESS of what Adobe does in the future, that have a problem with the CC model.