[yorwba]

Rereading that, I should have worded it as "those are skills that are required for Deep Learning research". There are of course a bunch of other skills you need to be successful, but you won't get far without being comfortable with linear algebra and calculus.

To answer your question, I believe that because I haven't yet seen a Deep Learning paper which did not couch its results in terms of those, even if it might not have been strictly necessary. If you do not understand the basics of current approaches, you'll have a hard time developing them further.