Why are non-emitting particle systems cost me extra SetPasses?

I'm having a couple of particle systems parented under gameobjects in my scene. They have playOnAwake set to false so they won't start playing until certain events trigger them. However, even though they're not emitting, profiler still shows a couple of extra SetPasses for them (something that causes performance issues on limited resource platforms such as mobile VR). Why do non-playing non-emitting particle systems cost me those extra SetPasses?

Note: the reason I say they cost me extra SetPasses is that SetPass number in Rendering drops when I remove these inactive particle systems, and goes back higher again when I re-add them.