Livre d'Or

Yes, I definitely see the wisdom in this. There are sometimes practical reasons against it, of course, a big one being financial; if you do a PhD midway through your career, when lots of your peers have decent incomes, it's much harder to be frugal than when everyone you know is straight out of university and used to student standards of living. And if you have a family or long-term relationship, it's appallingly disruptive. But I think the big thing about having worked a bit before starting is that you know there's life outside academia, you know that the worst thing your supervisor can do is throw you out, and if that happens, you can still do something (hopefully) worthwhile and get paid. And yes, I can well imagine that some maturity in managing the crucial relationship with your supervisor would be a help!