To me this is like saying, "Why did you rebuild this sports car? Normal cars get the job done fine." Or one I've been personally told: "Why install a custom OS on your phone? It worked fine before."
You may not see these improvements as important, but to someone with a passion for maps, it may mean a lot. I find that kind of passion for almost anything admirable. This guy hand-built a thing better than can be bought by map companies. That's pretty cool, even if you don't care about maps (I can't say I have a passion for maps, either). I couldn't give less of a shit about cars, in fact I hate them, but if someone custom built a car as a hobby exactly the way they wanted to, I would think that was really cool.