Perhaps it's something to do with proving one's virility. Yes, look at me, I'm tough, I live with a cactus. At any moment I could accidentally trip or drunkenly topple over and gently touch my arm to this spiny death-trap disguised as a knickknack, a gentle touch from which I may never recover. Yes. I flirt with danger. Aren't I butch?
--mezzogiorno ponders the deeper meaning of cacti as houseplants in a locked post.