This all tracks with my memory and experience (dev since the 90s). The other point that's missing to explain why it is so common is that one of the early Spols

This all tracks with my memory and experience (dev since the 90s). The other point that's missing to explain why it is so common is that one of the early Spolsky articles that got a lot of attention at the time (early 2000's) and was very influential asserted that the two areas of programming that seemed to "separate the men from the boys", so to speak, were pointers and recursion. Ie, independent of how long someone had been programming or what language/domain they mostly worked in, there was a tangible rift between developers who deeply understood and could use those concepts and those who didn't. If someone was comfortable with pointers and recursion, it was considered a safe bet that they could pick up pretty much any other concept/language/whatever without much trouble. Implementing linked lists was a good demonstration that you could probably deal with the basic concept of pointers. Spolsky's argument was probably also born from the same experience of the industry at the time. Before the first big dotcom boom, pretty much anyone applying for a programming job who had a CS degree or previous job as a programmer could mostly be assumed to be basically competent. It wasn't a lucrative field so it self-selected for people who could understand "difficult" concepts like that. Anyone who struggled too hard with those would've changed majors or found easier work for better pay. It was mostly HR and managers doing hiring and it mostly worked out because of that natural filtering. After the dotcom boom, when programmers were seen to have high salaries or become early millionaires, the market was flooded with developers with inflated resumes that could talk their way past non-technical interviewers but really had only "programmed" some HTML before and would struggle to write a hello world program in Perl.