[booticon]

My understanding of it is that they're working within the constraints of WebKit in iOS. Developers aren't able to update the icon in realtime, but if you have a homescreen webapp it can update the icon each time you launch it. This is a nice workaround, since I used to launch my homescreen weather app every ten minutes, and chances are the temperature hasn't changed much since the last time I checked. I say "used to" because I use the Weather widget in Notification Center.

[thereallurch]

Is there something I am missing? Why would you be checking the weather so often? I agree that this is a novel use of a site icon, but it has limited (minimal) advantages.

[booticon]

For me apps like this can fall into habitual use, almost approaching muscle memory, e.g. checking e-mail/Twitter.