Where's the fun in that? Building your own PC is a thrill - budgeting, chosing components, excitedly waiting for each to arrive or picking them from shelf, assembling everything and then pressing the power button to power everything up for the first time. Followed by your heart sinking when nothing happens "ohfuckohfuckohfuck, did I I just burn something out - there isn't any smoke, but I hope it's not the processor". Reseat everything, reconnect cables, get an some sign of life, but it's an error code - progress. Multiple attempts at fixing the error and finally get a POST screen. Apple can't sell that emotional experience or sense of ownership - self-built machines have a personality.
The extra RAM and/or cores I get from a self-build vs. equally priced Apple computer is just a bonus. Modern standards make surprise incompatibilities less likely than in the past, looking at the specs works 99.9% of the times
I honestly had to laugh at the lack of progress in the area.