the microsoft process cost for many individual patches versus larger collections isn't the real issue. behind the scenes, it should be essentially the same. it is a real issue for customers, particularly in IT, to deal with and manage all of those micropatches. especially in a world where you are responsible for validating every patch against your countless internal apps, deployments of updates are not trivial, and you have scenarios like finance where there is SOX compliance, auditing, etc. this is why the model of patch tuesday and the predictability of knowing when the patches were coming (regardless of number) and ability to plan your testing & deployment was loved by IT departments.

the additional tradeoff you need to consider is that the smaller you make the patches, the larger the number of variations you need to test for later patches, updates, app compat, etc. that is why service packs were a thing - you could baseline after a period of many patches getting out there, and start the process again.

(full disclosure: I used to work on and around some of this at microsoft many moons ago)