Because there is no reasonable basis for stating it will save money. The only possible argument you could make, that the state could refuse to raise their pay and benefits, it's something they can also do if the union exists. Getting rid of the union may make it easier on them, but the ultimate control of the purse belong with the state government.
Okay, so let's take that scenario, and do a little logic game with it.
- State tells union it will be cutting wages.
- Union says no.
- State refuses to budge.
- Union goes on strike.
- Strike causes undue hardship on State and non-union member citizens.
- Strike ends in either the Union giving in, or the state having to find somewhere else to cut that is even more painful, but has less special interest protection.
- Taxes increase or services in other areas decrease to cover the unfunded budget.
Now, without collective bargaining (as with FEDERAL Employees)
- State says they're cutting wages.
- Workers say screw that and start looking for other jobs that pay as well.
- New workers are hired to replace the old one who quit
- Nobody except those who quit without finding better jobs experiences any duress
- Taxes and spending stay down.
Pretty simple situation in my book. No collective bargaining allows the public sector jobs to go back to market supported levels as should have always been the case.