But to answer your question -- the reason IMO to learn the fastai framework (or indeed any software which incorporates a significant amount of novel research) would be to learn about the new ideas that it introduces, in order to become a more effective and informed practitioner. And if you find you like it, you may even decide to use it.
I feel that while this course is surely superb, I don't want to invest time in a new framwework. What's your opinion?
We've got lightning, fast.ai, and another one that I forgot about... why?