We have two tags for grammatical voice:
And we have exactly 18 questions tagged with the latter.
But every single active voice question also mentions the passive voice!
It doesn't really make sense to split these up. These questions are generally about the relationship between active and passive—the grammatical relationship, the semantic relationship, or both. And even if we have a couple questions that really are about the passive voice only, we don't need a separate tag for the active voice.
Theoretically, we might want a single tag called "voice", but that wouldn't be very helpful for our users; linguists might call this a system of voice, but I think most people will probably try typing in "passive" first and "active" second.
So let's merge them into a single tag called passive-active.