Maybe. I think that if we see poor people systematically playing the lottery more often than well-off people do, differences in utility functions are at least as good an explanation as differences in intelligence.

• If utility functions are sigmoidal, this in itself would predict poor people to play the lottery much more often than rich people.
• The "poor people are stupid" explanation says that poor people are less likely to grasp how small the probability of winning is. I'm skeptical that IQ 100 or even IQ 115 people grasp such small numbers any better.
• Crack use is high in neighborhoods where people are not just poor, but have a high probability of dying or ending up in prison. Look at the Sandtown Health Profile 2008. A person in Sandtown has a 1 in 6 chance of dying before reaching age 45. For males, it's higher. A man who "lives in Sandtown" is more likely to actually live in prison than in Sandtown. I didn't cherry-pick Sandtown; I chose it because my mom used to work at a day care there. A man living there, deciding whether to take up crack, has fewer expected years of good life lost than someone living in Fairfax.

In general, when we see one group of people consistently engaging in higher levels of behavior that seems irrational to us, there's a good chance that something in their environment makes that behavior more rational for them than for us.