It's envy, mother of hate. Old money envies new money because new money actually earned it rather than inheriting it.
I agree, but why would you want to have neighbors who don’t want you? A pretty expensive point to make.
More to the point, "new money" has demonstrated the ABILITY to earn money. "Old money" just inherited an ancestor's money, but not necessarily the intelligence, drive, and energy which enabled the ancestor to create that fortune. For many, it may be the bitterness which comes from the knowledge that if they ever lost their fortunes, they would have difficulty holding a minimum wage job.