It's catnip for the part of the HN audience who thinks:
1/ I am smart at computers and basic maths, so I must be smart on an absolute scale.
2/ I can't understand this easily, so therefor it is obviously broken.
Much like "timezones are hard, therefore wrong", "why should I learn other human languages, they don't work like I expect", "running a society is harder than telling a computer what to do, so people are stupid".
Music is an interest of mine, but not an active obsession. I've learned songs I want to play only through tabs, because every time I attempted to learn sheet music online, I ran away out of the fear of the heavy fog that exists in most descriptions about sheet music. Not to mention insufferable smugness, much like wine and craft beer snobs, about how sheet music is superior.
This guy, on the other hand, kept my attention, and described it in a way that I honestly found worth my time. I read the whole thing without wanting to switch tabs or multitask.
Which is great! That's why i read HN basically.