I've not read Friendship is Optimal, nor will I, but I am aware one character smokes for the nootropic effect.

Given the tendency for optimisation, self-experimentation, and weird medical interventions, I'd expect to rank motivations for smoking in this group in the following way:

  1. "Aaaaaaa, we're all going to die! I need something for my nerves!"

  2. They read a MLP fanfic about an AI taking over the world and were inspired.

  3. They think their AI will actually solve all the problems.