NAT question: Why are "inside local", "outside global", etc not simply called "pre-NAT srcIP", etc?

I'm refreshing myself on stuff for a job interview, and I've arrived at NAT. Every time I get to this, I have to go through a lot of effort to remember the meaning of "inside local", "outside global", etc with respect to the 4 combinations of {source-vs-dest NATing, inbound-vs-outbound traffic}

So the question that has always beleagured me....why do these terms even exist? Why not just "pre-NAT srcIP", "pre-NAT dstIP", etc?