Different people could name many reasons to learn how to write documents using this software. I'm not going to argue that in TeX one can faithfully reproduce 16th-century bibles, or automatically generate diplomas or envelope labels. My argument will be focused on the average user, who most likely uses MS Office and does not want to learn other superstructures. I will make one single argument that I think carries enough weight to outweigh the power of the MS Office.
Did you hear the joke about what happens when you move a picture in Word? I admit it's not a very funny joke, but I think it reveals some truth about Word or other office programs. These programs are supposed to be made to be user-friendly, but that means you have to somehow make all the features tick. This is often frustrating when you don't know how, for example, to make a list that would be momentarily interrupted, a fixed space or said image manipulation. And looking for meetings on the Internet is out of the question for bad documentation. When Word formatting is done, one does not feel that one understands how the program works, but that one has achieved a fragile equilibrium that must not be broken in the first place; it is a kind of magic. In LaTeX, on the other hand, you can do almost anything, and if you can do it, you've learned something, and you can apply that technique next time. The documentation is readily available on Stack Overflow, and I have yet to encounter an intractable problem. Using LaTeX will save me a lot of anger and time.