I'm not sure whether or not there is a correlation here. Anecdotally, it seems to me there are plenty of wealthy, employed people who buy new cars and crash them after drinking.
But even if it is true that those who drive cheaper, older cars are more likely to drive drunk? Today's new cars with high-tech self driving features are tomorrow's affordable used cars. You have to start somewhere.
It seems unlikely that people who buy/use early self-driving cars have the same percentage of drunk driving as the general population. Surely employment rates would be a factor, for example.