A common request from Apple Watch users over the years has been the ability to use third-party watch faces, but watchOS 10 still does not support this. In an interview with Swiss newspaper Tages-Anzeiger published today, Apple’s VP of Technology Kevin Lynch and product marketing employee Deidre Caldbeck explained why.

The interview was spotted earlier by 9to5Mac‘s Benjamin Mayo, and the quotes below are machine translated from German.

Lynch said Apple puts a “huge amount of effort” into every watch face to ensure they work “uniformly and simply,” and said Apple needs to plan ahead to make sure watch faces continue to work “if we want to change something or add new possibilities.”

Caldbeck added that developers are able to create complications for their watchOS apps, which adds a layer of customization to watch faces by allowing for glanceable information to be displayed, such as a CARROT Weather forecast. Starting with watchOS 10, the new Smart Stack widgets feature offers space for up to three complications.

That’s everything Apple had to say about the lack of third-party watch faces in the interview, which touches on several other watchOS 10 details.

watchOS 10 will be released later this year for the Apple Watch Series 4 and newer, and is currently available in beta for users with a free Apple developer account. A public beta is coming in July for users who do not wish to use the developer beta.