Learning By Doing.
Successful marketing, they say, is dependent on understanding your customers. Implicit in that is the need to understand how people assimilate information, about how they come to decisions, and about how they learn.
One part of that is to submerge yourself in learning theory and the psychology of persuasion and behavioural change. Another, I've discovered by chance recently, is to learn something new. Something that has nothing to do with your work and which preferably you can learn with a group of strangers and a number of teachers.
It's a humbling experience and that's reason enough to do it. But you'll also come to appreciate the peaks and troughs of learning; the variety of teaching methods, personalities and vocabularies; the ones that work for you and maybe why they do and others don't; and you'll witness all of the above as it relates to a random group of people.
I won't labour the metaphor, but as well as learning what you went there to learn, you'll also learn a lot about communication and the absorption of information, not to mention your own intellectual prejudices. And, best of all, you'll be doing it in real life rather than in a focus group.