This is how I see it: Take someone making $50,000 and someone making $5,000,000 per year. To the first person, $1000 is $1000, but to the second person, $1000 is more like $10 due to the income difference and this is why you see rich people tip more, they really do see the $100 as $10. Tipping should be done 100% dependant on service and service alone, if I was rich enough I would take part in sob stories (medical bills, single parent) but until then I only tip on great service.
To answer your question, no they should not tip more just because they are wealthy or have the means to. If that's the expectation, when will the begging stop? And when was the last time a famous person had to pay for anything, I'm pretty sure everything would be comped by the manager.