I think it's silly to generalize like this, and base how someone turns out later in life on whether they received an allowance. There are far too many factors involved, and allowance is a symptom more than a cause.
IMO, the single most important thing is what values your parents pass on to you, not whether they give you free money. Believe it or not, you can learn responsibility and get an allowance, and still turn out fine.
I also laugh when I hear people throwing out statistics (like 85% of rich kids "suck in life"). I'm sure you reached that conclusion through some serious scientific research.
The premise that spoiled kids that got stuff for free become failures, and poor people who had to work hard to get where they are become successful, is ridiculous.
I'm going to go out on a limb and say that roughly the same percentage of poor and rich people turn out to be respectable people, regardless of their background.