(1) Paypal wasn't around when the MIT team of fame was in Vegas. Neither was electronic money transfer in general. So that's a good reason why THEY didn't use it.
(2) The number of Americans who pay a 40% tax on anything is ridiculously small. Since the 70's, the maximum federal income tax rate has gone from 38% to 35%, so even if you made an infinite amount of money, you'd never have an aggregate 40% tax rate. But even if you're in the "35% tax bracket", you DON'T pay 35% in taxes. You pay 10% on your first $10,000 or so, then 15% on the next $40,000, then 23% on the next $100,000, etc, etc. So as your income approached infinity, your tax rate would approach 35%. In 2005, the median American paid an aggregate federal income tax rate of 14%. The median millionaire paid about 25%.
There is one tax that's higher, the inheritance tax (currently suspended or reduced), which can tax up to 50%. But again, it's only 50% in excess of a certain threshold - somewhere around $1,000,000 IIRC. So if you inherit $1,100,000, you're paying about 5% of that in taxes. If you inherit $2,000,000, you're paying about 25%. You will need to inherit $5,000,000 before an inheritance tax reaches the 40% threshold.