Basically because there are more reasons to keep it as is rather than nerf it.
There is so much that the devs could do with counters to empowered. Like more troops with traits that explode gems at beginning of match or even revamp some older troops traits’ to bring them up to date. Maybe even an empowered troop trait that drains 1 or 2 mana from 1-4 troops etc . The possibilities are out there . I like empowered troops btw and don’t want them nerfed ,but wouldn’t mind some more variety in future traits is all.
Don’t worry, there is no reasons for them to remove Empowered.