I agree with this. A few years ago, I was making half (yep, half) what my coworker was making ($10/hr vs. roughly $20, part time). Her credit rating was bad enough that she couldn't have a credit card, so borrowing wasn't the problem. I was determined to sort out her shit (I like to meddle in other's financial affairs, what can I say?) and had her go through a basic task: document every expense, no matter how small. Within a week, she became so embarrassed by the stupid, pointless crap she was blowing her money on that she ended up with numerous hundreds in her savings account at the end of the month, because she skipped all those one-day boredom toys.
Naturally, the type to blow all their money on stupid shit isn't the type to stick to a mid- or long-term financial planning scheme, but the anecdote does lend some evidence to the "stupid shit" theory.