Safari pinned tab favicons

In a post on Daring Fireball today, John Gruber makes a convincing argument for Safari showing favicons in tabs:

With many tabs open, there’s really nothing subjective about it: Chrome’s tabs are more usable because they show favicons.

Even more surprising to me is that Safari doesn’t use favicons for pinned tabs. Instead it uses a special monochrome vector icon. Ever since adding favicon support to Micro.blog, I’ve had on my to-do list to create one of these vector icons for Safari, but so far I haven’t been able to justify the effort. (And judging by a handful of my favorite sites, no one else has bothered to create a pinned tab vector icon either.)

Why does Apple require a separate icon format here? Probably for the same reason as John Gruber’s guess about normal tabs:

I don’t know what the argument is against showing favicons in Safari’s tabs, but I can only presume that it’s because some contingent within Apple thinks it would spoil the monochromatic aesthetic of Safari’s toolbar area.

It seems clear that these pinned tab vector icons are a dead-end. There are already too many sizes of favicons. Safari should have basic favicon support in tabs and do it with as few extra icon files as possible.