When a resource is expensive, it seems sensible to use it as efficiently as possible. So we batch jobs up for it, making them wait, so the expensive, and therefore scarce resource can be used to the max.
The problem with this approach is that it distorts the process, optimising a single step at the expense of the rest of it.
This distortion often persists long after the resource in question is no longer scarce. So you get GP and hospital waiting rooms; jobcentres and jury rooms, full of people in forced idleness, just so that the ‘scarce resource’ is maximally productive.
What if we designed our processes around the most critically affected role instead?
Things would look very different, and would be much more efficent overall - although the ‘scarce resouce’ might feel a little less important.