Reducing buffer size puts back pressure on the whole system, which can be valuable to manage load (but often throttles faster stages and that throttling makes people uncomfortable). A meaningful metric is how much of the buffer is used at any given time and the throughout. If the buffer is backed up, that says there's a bottle neck on the consumption side of the buffer and more bandwidth is needed there. For whatever reason, adjusting buffer sizes is the more common action taken. A buffer provides throughput management but it also provides info/metrics about the operation of the system.
replyYou can also observe this in games like Dyson Sphere Program, (which is all workers and queues and buffers) where adding a buffer storage section of a belt only hides the fact that you are under-producing one of the components required.
replyThe buffer smooths out bursty flow but you don't want that in the middle of the pipeline, as it actually represents mid-pipeline inefficiency. You should actually be fixing the upstream or downstream problem.
[1] or other automation games like Factorio, Mindustry
I'll note that speedrunners absolutely buffer mid-pipeline in Factorio, and not just for hand-crafting purpouses. Sometimes you're waiting for R&D, sometimes you're just running half the machines for twice as long, giving you the same output while saving on build costs. The actual bottlenecks are constantly shifting. "I'm not speedrunning!" you might say, but every regular game could've started as a speedrun that could've gotten you to where you are faster.
replyUnderstanding the tendency of mid-pipeline buffers to hide problems is useful, but scorning them entirely is also suboptimal.