My point was that a machine is always intended to make some useful work, and even as a sole developer of a private project, that project still has one enduser,

My point was that a machine is always intended to make some useful work, and even as a sole developer of a private project, that project still has one enduser, the developer itself, since the existence of the project is to achieve meaningful computation one way or another, even if that computation is performed only in the test suite, hence the enduser as root. However, as a project organizer, sure, you want to strive for welcoming others, making it easy to embark, 1-cli command to setup, interesting to engage and persevere in development, and so forth.