Using the numbers in this article[1], 1% of the taxpayers make only about 24% of the total income in CA, not 80%.
[1] http://www.sacbee.com/site-services/databases/article9349178...
[1] http://www.sacbee.com/site-services/databases/article9349178...
For the other 76%, all of that income may be spent on just food/rent/other essentials. Whereas the 1% have excess that they can save, or spend on luxuries. That's why tiered tax regimes exist.
NB. The definition of "needs" is obviously very debatable. The top 1% in California is defined as ~$90k, but given a median rent of >$4000/mth in SF, that skews the needs/excess taxable money argument considerably.