Earlier quoted context omitted.
There's nothing different from any other extension, so what you're saying nobody should be using extensions in their browsers. Good luck with convincing people not to do it.
Well, I for one don't use any extensions with Chrome. And not even from security concerns. Just from lack of any interest to do so. Why should I? For some marginal utility? I'd take it more average people don't use extensions either -- if they know what they are in the first place.
Yes, this is the point of extensions. Extensions are help you and others do things with the browser that the vendor shouldn't really spend time on. Approaching them with the idea that they're useless doesn't really help your argument.
For example, I once wrote a browser extension that extracts class calendar info from the school website and automatically syncs it to the calendar application of your choosing. It turned my class scheduling process from an error-prone 2 hour process to a 3-click 10 minute step. You can label that as a useless, marginal utility, but that's being facetious at best.