Depends what's meant by 'developing Fe'... if you mean developing the ability to be more aware of other's feelings and to behave in a more considerate manner, I don't see how it isn't obvious why this would be worth learning to do, however difficult it might be...
If you're talking about ACTUALLY caring about other people, I don't think that's something people do learn on purpose, but I can say that my attachment level in that sense to the cares of other people has become greatly augmented both from what it used to be and what's 'normal' for my type. But I didn't deliberately set out to 'learn' that... it's just come naturally as a side effect of other areas in which I've more deliberately developed. As I made more of an effort to cultivate the more shallow aspect of Fe, I found that I got to know people in a way I hadn't before, which led to developing a greater understanding of them... that in turn led to a greater sense that actually, I'd greatly underestimated 'people' in general all my life, and much of the reason I had previously been so detached was because I considered most people not worth attaching to. As I understood more people more deeply, having this opportunity 'bought' for me by deliberately showing better manners and consideration, thereby making people trust me more and more willing to open up to me, I realized that part of the basis for my previous detachment was actually false, and that in fact many people who I would previously have considered not worth attaching to, are actually very much worth it.
That in turn has led to a greater appreciation of humanity in general... and on and on...
edit - I'm not quite sure how this connects with the 'expressing/showing your own emotions' side of Fe... I guess I have started to show them more, but I'm still a bit of a cow with a gun about it all, don't really understand them myself... possibly due to Fe developing way ahead of Fi?