That’s a rather narrow set of use cases. For example, they are audio and video editing powerhouses. Audio in particular is exceptional because of core audio in MacOS.

And upgradable components aren’t something 95% of the population is worried about. Max out what you need when you buy it. My last Mac lasted 8 years with no trouble. And by the time I was ready to upgrade, the bottleneck was mainly the cpu, which in a case of 8 years, that means a new motherboard, and at that point you might as well upgrade the whole computer, as standards have changed and updated.