This link (of a different picture) may give you a hint of why they were invented in the first place:
If you can't open the link (or can't figure out what the picture (in the link) means) for whatever reason, they are created to help the blind and visually impaired to direct them where to go and where not to go.
From what I read? They were originally called "Tenji" blocks.
I see them in the bigger towns but not out here in the sticks but when I was in California recently, they were everywhere.