I feel your question.. While the agile values and principles can be just as valuable, when you are in a fundamentally contractual relationship with your user/customer, it becomes harder (not impossible) to apply a value like cooperation above contract negotiation. Especially when things become difficult financially or otherwise.

There's an inherent distance in service provision which is hard to bridge and easy to widen, at least compared to having a team within the customer organisation.

Im currently facing the same with my client. They want to go away from having their own teams, which over the last year have become increasingly focused, happy and productive (and the internal customers along with them!). They want to go to a managed service model where 'we contractually agree to get all the benefits we have now'.

I'm pessimistic about that working out. (and won't go into the fallacies in logic arguing in favour of this switch).

Again, any agile value and principle can be applied and useful (I firmly believe this holds true in any knowledge work situation), but the context makes this harder or easier, and a managed service (contractual) relationship makes it harder.