Macworld:

There’s still one major place that Apple could stand to relax its rules: letting users choose default apps for tasks like mail, calendaring, and web browsing. For users, the benefits of choosing default apps is obvious.

Not everybody is going to switch to a third-party app if this happens. Most people probably are probably happy enough with the defaults. But for those folks who want a feature that Apple’s apps don’t currently have—like snoozing mail message alerts or sync between Chrome on iOS and your PC—the choice to use that app as the default should be available.

As a photographer, I’d love to be able to change the default photo app and I’d love to change the default mapping behaviour to a different app as well. The vast majority of users are unlikely to ever do this but for “power users” of one sort or another, it would be a nice feature.