Antique frames and lockets are both fragile things. Antique frames, for obvious reasons, go great with antique photographs because there isn't any abrupt clashes of style. Antique photos look right at home, which is fitting, because they're evidence of memories that most people like to surround themselves with in their personal spaces.
But a person can't stay inside forever, lending to the popularity of lockets. Hypothetically, a locket allows you to safely carry a picture around when you're not at home. Many lockets however, break extremely easily, and are a hassle to untangle once they get messed up.
Watches are much easier to handle because most of them don't have links, so they don't get tangled. Their bands are thicker, so it takes a lot more for them to break, and the watch face is usually much larger than the storage in a locket. With how decorative watches can be now-a-days, they can also be a much prettier alternative.
So the next time you're thinking about finding a new way to display your photos, or want a cool DI for that antique watch you found, consider putting them in a watch.