At the end of the month, after taxes and FICA and health insurance and Medicare and retirement are withheld, and after paying for housing, food, transportation, insurance, utilities, sundry expenses, and student loans--there's not a whole lot of that $100K/12 left!
Raising taxes on $100K would be almost intolerable. I could probably part with a couple thousand more a year, but it would be difficult, and I have very little faith that they'll invest my money wisely....