For example, to do his job well, a client of mine needed to learn some electrical engineering. Rather than recommending he go back to school for a certificate let alone a degree, I encouraged him to find an electrical engineer in or out of his workplace who is willing to answer his emailed or phoned questions when he gets stuck.
Learning on a need-to-know/ just-in-time basis is so much more time-effective than taking a course. In the latter, you're taught a mountain of content, most of which you'll never need, and what you will need, you'll long have forgotten by the time you need it. Oh and of course, courses are much more expensive and time consuming.