Not often, as you say. I have to assume that Apple has telemetry on how much certain features are used, at least at some sort of statistical level, and takes that into account when weighing the development and testing cost of keeping a feature around.
These polls won’t be statistically significant, of course, because TidBITS readers are undoubtedly a specific segment of the market. But I just have to know, has anyone ever used Launchpad? :-) (Probably, but I’ve never seen it used in the wild or even heard of anyone using it.)