Creating a QR Code step by step

I appreciate the steps, but this fails to answer a question which, imho, is way too often omitted in tech tutorials, and that’s ”Why?”. Sure, I understand these are just the steps to create a QR code and I could just Google why the QR code needs a masking pattern, but that’s besides the point. A good material would explain why I need it, instead of just saying it should be done. Even one sentence would be sufficient.

A while ago I found a generator that took an image and a text and tried to use a genetic algorithm to evolve a QR code that looked like (a 2-bit dither of) the image. Unfortunately I’ve since lost the link, but I was quite impressed that it managed to generate a QR code for my then-employer’s URL that looked like their logo. Impressive what’s possible with a lot of error correction.

Unfortunately it seems that every online explanation of QR codes always leaves out the Reed-Solomon error code calculation. The author here describes it as “long, tedious, and not very interesting”, but since everyone seems to think that, it is now very hard to find.