You can also be a good, e.g., mechanical engineer without getting an engineering degree, but this is an exception to the rule.

Also, companies use the degree as an indicator of skill, so the good engineer who doesn't have a degree needs to somehow reliably demonstrate a solid understanding of the field to compensate. Obviously, from the company's point of view, one is easier to deal with than the other.

The same applies to PhDs and research. A PhD proves that the person has followed through with and understood a very precise topic of research for 2-3 years.

> You can also be a good, e.g., mechanical engineer without getting an engineering degree, but this is an exception to the rule.

That's an awfully incorrect analogy. Enrolling in a PhD program has absolutely nothing in common with getting an engineering degree. An engineering degree is conceived to give the students a pre-established set of skills and technical knowledge that meets industry demands.

A PhD program is set to help the PhD candidate research a very precise and specific topic, which more often than not is entirely irrelevant to any industry, so that in about 4 years he is able to produce some scientific findings and defend a thesis in front of a jury.

The key difference is that an engineering degree is tailored to teach marketable job skills while the PhD program is the exact opposite.

> That's an awfully incorrect analogy.

I would say "not entirely accurate", rather than "incorrect". Are you familiar with what happens in PhD research and the skills you can acquire during a PhD?

> [.،.] so that in about 4 years he is able to produce some scientific findings and defend a thesis in front of a jury.

And that's exactly what having a PhD proves: that you can start from a cursory understanding of a topic and end up contributing something novel to the field.

Given that industrial research requires you to do practically the same thing -- albeit in a more applied fashion -- a PhD is usually a good indicator when hiring for such positions. Again, there may be more suitable people for the position who don't have PhDs, but that is once again an exception to the rule.

> Are you familiar with what happens in PhD research and the skills you can acquire during a PhD?

Yes, very familiar. I've worked as a researcher in a public university and enrolled in a PhD program, but I dropped out after it was made patently clear that the whole thing was a complete waste of time.

I even had my advisor pressure me to continue working for the research group with scare tactics such as warning that getting a job would be virtually impossible and working for the research group was my only viable option.

> And that's exactly what having a PhD proves: that you can start from a cursory understanding of a topic and end up contributing something novel to the field.

...and that on its own is worth absolutely zero. You either have marketable skills or you don't, and a PhD degree does not help a PhD candidate develop marketable skills, It's years of drudge work for a research group that managed to get funding for areas which more often than not are entirely irrelevant. To develop marketable skills the PhD candidate needs to devote extra time that he doesn't have to go out of his way to make himself relevant as a job candidate.