These clauses are aggressively anti-librarian, and unfortunately librarians don't have a choice but to subscribe at whatever price. Academic papers don't exist in a competitive marketplace; once a non-open access paper is published it's considered part of the permanent academic literature, which academics are professionally required to read and cite. Yet each paper is only available from the publisher that owns its copyright.

It's no wonder why Elsevier draws such ire from the librarian community... an analogy would be if a company legally disallowed its employees from discussing their salaries with anyone, in order to reduce the information available when any other employee negotiates a salary or raise.

And even though David Tempest argues that the main reason for these clauses is to maintain price differentiation between countries, I'd guess that this policy is equally designed to convince small but well-funded US research institutes to keep their non-discount subscriptions, while giving relatively steep discounts to large accounts like the UC system that have negotiating power due to their size.

Fundamentally, the ecosystem of subscription journals is full of non-market dynamics and requires extensive legal management (think NDAs, copyright transfer agreements, DMCA takedowns and copyright infringement enforcement). On the other hand, the rise of Open Access journals has produced a healthy competitive market, where authors can choose where to publish based on a variety of factors including cost, quality of peer review, user-friendly submission tools, and prestige of the journal brand. Plus, copyright is largely a non-issue for open access: authors keep their copyright and there's no cost to the publisher for enforcing against infringement.

I think the more market-driven nature of OA, plus the obvious desire to have publicly-funded research be publicly available, will compound its growth and cause it to eventually overtake the subscription journal model.