User blog comment:Roygbiv666/What are Splicers splicing?/@comment-1330314-20100815165621

Yes, it seems to be mainly Gene Tonics. Gameplay-wise, I think it's because the developers wanted to focus all of the plasmid usage on the Houdinis, but story-wise I think it's because that's what everybody started splicing with anyway. Being able to set people on fire doesn't have any real use in normal life, but a Gene Tonic that cures your baldness does. Scientists took tonics to become smarter, sportsmen took tonics to get stronger, and most people used it to fix whatever they didn't like with their own bodies. And after Rapture went to pot, most people probably couldn't afford plasmids.