The difference between vain and nice is in the bearers heart.
We can't see into Bill Bennett's heart, so we can't know if he was showing off his wealth. I assumed he was, but that's only an assumption based on the amount of money and my generalizations about high rolling. There is also a difference between leaving large tips and high rolling (like the ones I described above).
In the end although we can't see into Bennett's heart, we can say he tested his virtue, and perhaps tempted fate by dropping such large amounts of cash it would be hard not to show off.
You seem to be assuming that all wealthy people are rude, that "high rollers" in general are a nasty bunch of people. Doesn't wealth allow people to pay for services that are beyond the reach of others? And isn't the payment of services part of our capitalism?
I don't know how you can generalize in such a way. Again, it makes me think that you are fixated on his wealth, and assume that because he is wealthy, he is of low character.
Isn't it a sin to covet what another person has earned?