That is definitely part of it.

I often ruminate on just how much of what I learned in college and grad school I have completely forgotten... not so much the basic facts- those stuck with me - but the ability do the more complex calculations... I was really good at solving problems in special and general relativity, it was my favorite subject... now? I have forgotten all the vector and tensor analysis I used to have at the tip of my fingers...

I just don't use it in my job often... sometimes I have to apply something I forgot to my work... having learned it before means that I know where to go to relearn it, and I relearn it faster than if I were starting from scratch- but was it worth the years of intense stress and expense to get the formal education?

Yes, employers use evidence of formal education as proof that you have the tools needed to do the job- and to be fair they don't have a lot else to go by- but lack of a formal education does not mean you can't do the job, and a degree with honors does not PROVE you have what it takes... EVERY time I have taken a new job it has been totally outside what I have done before, and completely unrelated to what I did my graduate work on- the only common theme has been lasers.

As a student, I assumed whatever I worked on for my degree would be what I would be doing as a career. I clearly remember attending my first conference as a grad student and talking to a post-doc that had been involved in designing one of the instruments on a space probe to another planet... I felt deep disappointment in my choice of field, there was no way what I was working on would be of any interest for space exploration... I envied him and felt regret that I hadn't given more thought to the field I went into, instead of just stumbling into it. I had always wanted to work on space exploration, and wished that I had put more thought and planning to guide my career in that direction.

My graduate work was exploring how atoms ionize in extremely intense laser fields- intensities approaching 10^16 Watts per square centimeter. It was interesting, and it had a lot of mysteries that were not understood- but not a lot of obvious applications aside from understanding the physics better. When I finished my graduate work, I assumed that I would have to get a post-doc position and then struggle to get a position at a national lab or university. But at the end I was burnt out, tired of academia... my life was in turmoil. On a whim I applied for an engineering position I saw advertised at a national lab... it paid more than a post-doc, seemed interesting, and was on the other side of the country. It had little to do with what I had done as a grad student.

I got the position, and moved to Livermore California... and found out that the person I was supposed to learn the job from, the guy that had hired me, had had a nervous breakdown and quit. I was now the sole laser engineer in charge of integrating a 1500 Watt laser into the multi-hundred million dollar project. The laser I had worked on previously for my graduate work was- on a good day- just over 1 Watt.

After a few days of being paralyzed in panic I was able to pull it together and do the job I was hired for- I was hired essentially to be a laser technician, but after a few weeks I had accomplished the main task of integrating the laser into the system and was able to take on other engineering roles on the project...

Aside from working with lasers, there was very little overlap with what I had studied or worked on before- but my education did allow me to have a good idea where to go to learn the things I needed to know.

I would say that the most important benefits of the formal education were some degree of confidence that I could learn whatever I needed to know for whatever task I was presented with... and knowing where to go to learn what I needed.

Every job I have taken since grad school (3 different jobs so far, but my current job has been a long string of sometimes very different projects) has had little overlap with anything I have done before... every job has been the result of random chance, stumbling across an opportunity and applying on a whim- and without any long-term planning or strategy.

And now, 25 years after that chat with the post-doc that had me regretting my choices, I am working on space exploration... had I planned my career strategically, I rather doubt it would have worked out as well as it did... sometimes stumbling around and acting on the whim of the moment is the best course.

Formal education gives you familiarity with the tools you might need, or at least lets you know where to find those tools. You can get this familiarity without the formal education, of course, but it really helps. However, the MOST effective way to learn how to do something is actually doing it. You can read countless textbooks on lasers, for instance, but only by actually working with them can you develop the understanding an intuition needed to be able to successfully get them to do what you want.