Now here's the tricky bit:
With my pet care example, most of the tasks are going to have the same context, but what if that wasn't true? With a parallel project, a next action view would only show the first one, and if they are in a bunch of different contexts, it might not show me an action that I could do in my current context,
even though it is available, leading me to think that I couldn't make any progress on that project (a problem that wouldn't be an issue if I used the available view). Imagine that I'm at the office when I look at the views here and I think you'll see the problem.
If I'm looking at that project in the Available or Remaining view from some neutral point (not in any of the contexts which have actions), trying to decide where I should go first to make some progress on the project, I would probably go home, because that's the context of the first action on the list, which is nominally the most important, and that's the one shown. If I do the same with the Next Action view from that same neutral point, again, I would go home. But if I do the Next Action view while at the office, or running errands, the actions for that project are out of sight and out of mind.
This issue goes away with use of a SAL, at the cost of potentially putting more data on your screen. As it turns out, much of my SAL stuff has start dates and tends to get knocked off quickly in the morning, and coupling that with my preference for context views grouped by start or due date, I don't usually have to look at anything I'm not going to do, even when casting the relatively wide net of an Available or Remaining view.