Because people don't understand what these obligations cost:

pension_fund_withholding.jpg
This table uses after inflation numbers, which makes the returns appear small. In reality, CalPERS, CalSTRS, and most other pension funds, project a long-term rate of inflation of 3.0%. This means that the nearly best case scenarios here, 7.5% before inflation (showing as 4.5% after inflation on the table), are representative of the current official long-term projections used by most pension funds. Based on the official rates of projected returns for pension fund investments, a 30 year veteran, retiring on a "3.0% at 50″ pension, will collect 90% of their salary in retirement, and they will need to contribute 32.5% of their pay into their pension fund every year they work. On that basis, 9% is less than one-third what will be necessary to fund their retirement pension. But what if the pension funds return less than 4.5% (7.5% before inflation) per year?

As can be seen, for every 1.0% the real rate of return drops, the required contribution increases by over 10%. That is, if CalPERS can only deliver a 6.5% return (3.5% after inflation), the contribution goes up from 32.5% of salary to 43.4% of salary. If CalPERS rate of return goes down to a 5.5% return (2.5% after inflation), the contribution goes up from 32.5% of salary to 57.9% of salary.