The problem is that sometimes, you aren't really cut out for the PhD. Or the program burns you out. What then? What if you and your advisor have such severe conflicts that a PhD (or whatever) is not really feasible? What if your advisor just decides one day that they're not going to help any of their students become part of the community of minds, so all you have at the end of all this is a piece of paper and no meaningful contacts to get a job? In my case, I was still clinging to this idea that I could be a college professor, and it wasn't until I got the chance to exit with a masters that I started to accept that I wasn't cut out for it.
The problem is not that people end up with "useless" degrees - it's a rare day indeed that I do something even vaguely related to what I went to school for. The problem is that we as a society are addicted to blaming 18-24 years olds for not being perfect fucking fortune tellers when it comes to choosing a profession for the next 20 years, with an absolute minimum of data or tools to collect or evaluate that data. The problem is that we as a society say "you specialized in creating and operating specialized widget 'A', but while you were studying for that, the market shifted and now we only want specialized widget 'B', and the consequences of that market shift are completely and solely your burden to bear".
All of this to say that no matter how up-front we are about what the end of these long programs is, we are still, STILL asking people to make the right long-term decision, while insisting that they are also too young to rent a car because they won't make the right long-term decisions. "You're too young to buy alcohol, as you might make the wrong decision which could lead to an outcome that will haunt you for decades. Also, pick your career, right now. Delaying this decision will definitely cost you thousands of dollars, waste years of your life, and disrupt your social development (but picking wrong will have the same impacts, but magnified). It may bar you from certain housing situations. No, we won't help you meaningfully engage with the question, or help you understand the right questions to ask. You're an adult now, no one is going to hold your hand, take responsibility for yourself!".