Programmer Humor

Because I want to?

Well an uppercase ASCII char is a different char than its lowercase counterpart. I would argue that not differentiating between them is an arbitrary rule that doesn't make any sense, and in many cases, is more computationally difficult as it involves more comparisons and string manipulations (converting everything to lower case).

And the result is that you ultimately get files with visually distinct names, that aren't actually treated as distinct, and so there is a disconnect from how we process information and how the computer is doing it.

'A' != 'a', they are just as unequal as 'a' and 'b'

Edit: I would say the use case is exactly the same as programming case sensitivity, characters have meaning and capitalizing them has intent. Casing strategies are immensely prevalent in programming and carry a lot of weight for identifying programmers' intent (properties vs backing fields as an example) similar intent can be shown with file names.

Think the other way around: What's the use case for case insensitive file names? Does it justify the effort and complexity for the filesystem and the programs to know the difference between lower and upper space chars?

Suffering

That doesn't work, DS_Store are files not directories ( you need to use -type f).
An equivalent find command would be:
find "$HOME" -type f -name '.DS_Store' -delete -print
find takes a while; fd is way, way faster, but find is preinstalled, so there is that.