[tdeck]

The shorthand systems are mostly designed to be transcribed by the writer or someone very familiar with the writer's particular style, preferably while the information is still fresh in someone's mind to resolve ambiguity. Shorthand is mostly not a great system for long term information storage and it's not easy to quickly skim documents written in shorthand.

[kqr]

This is a common myth, but from what I understand of people who write in the more logical shorthand systems (without abusing custom abbreviations etc.) it's eminently skimmable, even long after the information is no longer fresh in mind.

[tdeck]

I don't know what you'd consider the more "logical" systems - there are only a few non-machine English shorthand systems with any degree of popularity. My own experience with Teeeline shorthand (which is a bit easier to learn, and I'm by no means good) is that I simply can't read quickly because I don't get much reading practice. Think about it: most of us read much more than we write. With shorthand, I only end up transcribing what I myself have written. So I'm slow at it.