Thats the problem. New mIRC users dont know how to deal with addons, dll and etc. So, "Why dont make it easy and add some feature with option to disable?".
Don't go there, I was using IRC in 1988. There is no reason why an application for any protocol has to have a certain look to it. I'm a GUI-junkie, easier to use == well organized; functionality need never be lost... And as far as speed of the app, a bunch of big scripts seem to slow mirc down more than I think skins would...