The browsers have been choosing very poorly and have a lot of bugs when
it comes to favicons. Using an ICO makes many browsers choose better in
most cases. Most large websites use ICO files.
The icons in the ICO file needs to be ordered largest to the smallest
icon, and due to a Chrome bug we are limited to 8 icons. This
unfortunately means we couldn't fit one of the Android sizes. The 72x72
icon was removed since testing showed that it was used the least.