I bet all these languages come from people with a thick CS theory background, and thus a tradition and a need to write formulae on a blackboard.
Unlike a keyboard, a blackboard is a graphical device, it's slow to produce long character strings, but basically any one glyph takes about the same time to write, be it an x, ≡, ∉, ⊕, ℵ, etc.
Then you want to plainly represent the same concepts in the computer language, et voilà.
This is a bit of a change-up from the usual "write-only language" complaint! But it does have the benefit of accuracy: yes, if you know the language, the time savings in writing APL are smaller than the savings in reading it. Both are faster, once you've spent a week or two with the keyboard, since even the slow method of typing a prefix character followed by a letter is faster than typing out a keyword in another language.
Array languages are rarely "product"s. While I do offer it to others for free, I make the language I want to use, and having nice-to-read symbols for a one-time tooling cost is a nice convenience for me. Don't call me thoughtless for having different tradeoffs than you!