It's related to the second usage model for XTU: Analyze.
The simpler the interface, the easier it is for people to use, and the more people will use it. If we require a mandatory screenshot for all users, the entry level becomes too steep, and users opt out.
We have requested a feature to include a screenshot (like Heaven), but we will probably not make it mandatory for all use cases. Maybe just for the top-10/20, which would affect the die-hard overclockers mainly.