Why buying a Linux machine is not such a simple thing
I'm somewhat considering buying a new home machine. If I used Windows, this would be an easy process; I could just go over to the local cluster of computer stores and pick up an inexpensive generic white box machine, or just buy something from Dell et al if I felt the need for a name brand. I wouldn't have to think about what components were inside the box because the result would invariably run Windows, although perhaps not without minor glitches; everyone builds things that run Windows.
(We're a university, so of course there's a cluster of local computer stores nearby. As for inexpensive, well, over the past few years it's become quite impressive how much computer you can get for not all that much money.)
However, I want a Linux machine. This means that I get to care a lot about what components are inside the box, because there is no way I can just assume that Linux will run on whatever random hardware I get, much less run well. Ignoring graphics cards entirely, there's all sorts of hardware where Linux either doesn't have drivers or doesn't have good drivers.
(And to be fair, a certain amount of this hardware is simply bad and would be a problem under Windows too.)
Thus I need the right components, and that means that I need to find out what the right components are, which means that I get to walk back into the ever-changing swamp that is PC hardware just so I can find out what hardware I should even start looking at. In theory I could settle for just 'has a Linux driver', but if I have to pick the components myself I might was well pick good components, ones that are known not to have odd failure modes.
(This process is not helped by the utter inability of the modern Internet search to provide useful links to good summary and feature comparison sites in between the 5671689 different 'buy here! boost our pageviews!' sites. I'll probably have to turn to Wikipedia to get a decent summary of the current state of CPUs and memory technology, too.)
All of this is, frankly, annoying and a hassle. The annoyance involved is one reason that I am still only somewhat considering replacing my home machine; after all, it works (more or less) and leaving it alone keeps my annoyance level down.
(Honesty compels me to admit that part of the problem is my perfectionist streak. Any time I spec out hardware I tend to get sucked into over-thinking and over-engineering the result; especially if I'm paying for it, I can't settle for a merely okay machine. I don't necessarily want the fastest and most powerful components, but I agonize over picking good ones and arranging everything just right. This is why I am unlikely to go into one of the local computer shops, get the current component list for one of their generic machines, and see if all of the bits work well enough under Linux.)