There was a time around 2013 when we started taking baby steps toward encouraging use of logo-only Activities. We even issued some product screenshots like that around then.
That is not our direction and hasn’t been since then. Many factors both on the ground and design-wise make it necessary to have names for Activities. So while we allow you to remove them, we think you should keep them. It looks better in the current design (we think), it definitely looks better in the future 5.X design, it is necessary for Alexa, and it is necessary for watchOS as well. In fact, if you don’t give Activities a name on watchOS, we go back and assume the default name based on the Activity’s device.
So, in general, keep your Activity names. If you at some point removed them, add them back.
Meanwhile, the forthcoming version 5 and associated Alexa enhancements does provide the ability to nickname devices and use those names instead.