Not sure what $- is meant to do in your short comment on it...?
As far as using your own scripts, it's true that your own scripts are often of more use to you than other scripts because it does only what you want/need and nothing else. I have a lot of my own scripts running. That said, most people are not programmers. They don't want to be and/or they don't have the logic (the mathematical definition of logic) skills required to be much good at it. There isn't any reason why we should ignore people who use other people's scripts just so we have certain features that can only help scripters and will hurt non-scripters.
Besides, I think that quote about the best script being your own is really meant as kind of a challenge to people to try and learn. That's just speculation, but it makes sense. It doesn't mean you shouldn't use other people's scripts.
Look at the typical $htmlfree identifier for removing HTML from text. Yes, it's not a large script by any means, but it serves as a good example without trying to think of some specific larger script. If that identifier does what it's supposed to do without problems, why should I choose to make my own instead of use what's already made? There are reasons to use scripts by other people. Or, look at really large (or full) scripts. I could make one, but I don't have the time or patience to do so. If I want to use one, I'd rather pick one that is good and, if needed, adjust it to suit my needs. Again, another reason why using other scripts isn't wrong/bad/etc.
It's good for people to learn to script. Do they have to? No. Should we ignore them just for a benefit to us that hurts them? No. Most people using mIRC don't script, or have very little skill in doing so. You'd hurt far more people than you would help. And I still see no reason why that space is so bad.
