Comment by LorenPechtel

And SVG means you can make a single file that contains everything. Pretty much irrelevant on the web, but we lack a good container format for putting a web page into a single document on disk.

I've done entire multi-layer maps in SVG, complete with clicking on the map taking you to any associated details. The part I never found a good answer for is when I wanted to use higher detail glyphs on higher resolution outputs. (Think of the sequence of lines typically used to represent stairs.)