I don't think that's all that horrible. If specialist tools require some training to use and have user interfaces that are extremely productive nobody bats an eye. A specialist keyboard for a programming language with very high productivity would make good sense.

Remember that when APL was created these things were not set in stone and what seems wrong to you in retrospect made perfectly good sense at the time (and in fact still makes perfectly good sense today, it's just that the world has moved on from APL to languages that are more verbose and/or that do not require symbols like these).

Math is another such language, and there is no keyboard suitable for entering mathematical expressions so we use software like LaTeX instead.

At least with the APL keyboard the link between input and display was very direct, with LaTeX much less so.

You're equating syntactic abstractions one-to-one with pieces of plastic.

What?