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The ~username convention in URLs, particularly older websites, comes as a result of web hosting practices in the early days of the internet, when many web servers would run on UNIX. Such systems supported multiple users, so this convention allowed every user in the system to have their own web space, accessible from the root of the webserver. This was especially common among the kinds of organisations that were early adopters of knowledge sharing over the world wide web (i.e., universities), as well as those giving access to everyday users wanting their own website (i.e., ISPs and hosting services), but the convention stuck around for a long time.