Or you can literally just manipulate your SVG through the DOM in an external JS script... I still have no idea what the original motivation behind scripts in SVGs was.
Yes, that was a large part of the thrust back in the day. Even if it wasn't officially a goal of the SVG working group, there was a lack of an open standards-based alternative to what Flash was able to do, and the developers of the SVG standard saw that adding animation/tweening wouldn't take much given what browsers were already becoming capable of.
I'm don't remember precisely but I don't think you could script it from the DOM, I don't see how that could work if it's a plugin.