How come subnetting is such a difficult topic? Seems pretty ambiguous

First of all, studying for my CCENT, then CCNA. So I'm trying to understand the basics. For the most part, I get subnetting. You use it to generate a number of networks using a single network. So if a client wants 250 unique addresses, you use subnetting to achieve that....

But why the pointless A,B,C network stuff? I was even told in /r/networking that these subnet types no longer even matter. So why learn them? Also, I totally get how the 255.255.255 translates to binary. it ends up being a series of 1's and 0s in each octet. But is this important to the CCNA test?

The CCNA covers subnetting, but seems very ambiguous what they want. They want a full understanding of subnetting history, mechanics, semantics, binary conversion, and all that jazz.... but it's not even all relevant apparently...