There's a version of Sparkle for Windows. I have no idea why apps don't adopt it.

I am constantly amazed and frustrated at how many apps I use on Windows have the following update process:

1. Pops up an alert telling me an update is available

2. I click a link in the alert opening my browser, taking me to a webpage full of links for different OSes and different architectures, which I have to search through to find Windows Intel x64

3. Wait to download the new version and then open it up

4. Spend 30 seconds clicking through a Windows Installer

Absolutely bonkers, especially considering some of these apps seem to release on an agile biweekly schedule. I usually procrastinate downloading updates because it's such a pain in the ass -- and that's not what you want your users to be doing.