SVG at least is old and has an actual usage: it's not pixel image, it contains mathematical instructions how to make a vector image.

Meaning the image scales indefinitely. A circle will always be perfectly round with it.

The text you see in front of your screen right now are vector graphics for instance.

Not at all. If you blow up a PNG 10x, for example, you can see the pixels plain as day. An SVG looks just as smooth at any size.
The reason why it isn't used for everything is because actually composing an SVG is very difficult. There's no way to make one for a photo, for example.