Thanks for your (as always) thoughtful comments Luke.
The qualities of usability you emphasize may in fact be part of an overall “sticky” strategy. It may not be that we are trying to make an online experience sticky for every visit, but that we are trying to make the overall experience of engaging with our online experience sticky. Perhaps that means enabling users to have very quick interactions so they come back often, not unlike the way a business that offers convenient parking may be more sticky (have greater customer loyalty) than one that is hard to get to.
In another example, offering offline/mobile access may appear to reduce stickiness, when it really may support an overall stickiness between an institution and its constituents.