Almost half a century ago (1971) Allen Tough wrote The Adult's Learning Projects. Terrible title, brilliant book.
In Chapter 5, he examines why adults learn and offers six reasons:
I think they're just right today. In fact, we have modern-day terminology for some of these eg just-in-time training for the first and digital badging for the last. Dr Tough says that one of these reasons dominates. I'm interested to know if that's still the case so I've set this up as an online poll - please take 10 seconds to add your opinion. Results will appear instantly after you've answered the (one) question. And I'll post the results on here soon.