Why are there no pack icons?

The issue with it really is consistency. Some of us -- myself, in particular -- are very anal-retentive about things looking the same or being neat and tidy. Having each pack leader create their own icon means there will be different styles, different levels of detail, and perhaps even different sizes, of icon. To me, having those sorts of icons all together would look really messy and busy, hence why we use the standard pawprint for all packs.

I myself have no trouble memorizing all the packs and their colours, but I'm also the one who makes the icons and sets up the packs so I'm intimately familiar with them all. Personally I would find icons harder. Knowing which pack is which does come with time, and if ever you're unsure of which pack is which, all you need to do is click on the pawprint and you can see which pack it is.