YMMV but I've also disabled favicons as well where I can.
For me the reason is that the icon is too small to be useful while browsing. The details are insignificant, so it just ends up being a "color" cue at best.
I actually hate newer versions of FF mobile that show favicons instead of the page title on the new tab page. I often have no clue what the icon of a site looks like before I stumble on that page or I bookmark it. Presenting me the icon without the text is like asking me a guessing game.
It makes sense for software packages, of which you have about 50 icons that you might be familiar with, but with web browsing it's easy to browse through that many websites in a day while searching for stuff, destroying any visual memory you might have.
Disabling it on mobile is sensible. In fact, I’m also currently using FF on iOS and will also do this (thanks to you I now know it’s an option). That being said, I still think 0.0000000001% of users won’t disable favicons (especially on desktop).
