No, there's no principle, there's a ~20 minutes old idea that we engineers are so obviously awesome that companies should actually be paying us for the privilege of interviewing us.

There may exists engineers obviously awesome enough for that to be feasible, and great for them (but they are probably also obviously awesome enough to not have to go through coding tests, so it's a moot point) and even if I could perhaps (judging by certain recruiter-emails) scrape by as one of them, I certainly couldn't five years ago.

Back then, if I'd had to be good enough on paper alone to warrant not just being put through the recruitment process, but to be paid for it was well, I am not convinced I'd have been considered (and yes, I did a take-home test, and I aced it and it made up for my near-total lack of on-paper qualities).

Of course, companies shouldn't waste their applicants time with needlessly extensive tests, but there certainly exists no 'principle' by which you have a claim to be reimbursed for spending a few hours on an application.