The current system for mime-type icons in pix/f that get displayed for different file types in the file picker and elsewhere is based on bitmap image formats. As a result it expects multiple copies of the file for specific pixel sizes e.g. we have

pdf-128.png pdf-256.png pdf-48.png pdf-72.png pdf-96.png
pdf-24.png pdf-32.png pdf-64.png pdf-80.png pdf.png

If you wish to use SVG icons for this purpose, you need to provide multiple copies of the same file with different names, which increases bandwith usage, load time, memory usage etc. for no benefit since the SVG is already scalable and is a bit of an annoyance when creating/updating the icons.