My PhD in Engineering was valued as a 500 pound increment over the graduate joining salary (12k) at the time. This was the IT industry in the 1980s. After that it contributed nothing to my advancement in a technical career. I would have done much better to have skipped the PhD and started 4 years earlier as a plain graduate and I would have probably increased my salary by 2 or 3k in those years. But of course, other industries and career paths, would have different outcomes. A PhD was essential for a University career. But in general you didn't do a PhD then for financial reasons. I doubt I would even go to University at all, if I was starting today, as I would not want the debt. On the other hand, one guy I studied with went on to fly the Space Shuttle, and he would not have done that, following his career path, without a PhD. It's a strange old world we live in and its hard to know if the choices we make are good ones until it is often to late to change them.
I dont know that it is a general issue of certificates. Obviously a PhD is important for a research or academic job in a technical subject but what is the relevance to a practical / industrial job? I recruited enough engineers but I would go near a PhD candidate for a maintenance engineer. Maybe it would be different for a design engineer but then I would be looking just as much for imagination / an ability to think laterally as I would for paper.
Your last sentence is absolutely right, not least because many of us dont really know what we want to do as a job until we have worked at a few we didnt want.
