David Shayer, TidBITS:

As an Apple software engineer, I worked on the first two releases of watchOS, so I’m familiar with many of the Apple Watch’s internal trade-offs. While I don’t have any inside information about current versions of watchOS and Apple Watch hardware, there are at least four reasons to think Apple won’t support third-party watch faces any time soon, if ever.

Read for the details, but:

• Battery life
• Buggy code
• Apple’s image
• Copyright worries

In a nutshell, handing control of Apple Watch faces over to developers would put the Apple Watch quality experience at risk.