Those vouchers are printed as a convenience for you if you owed over a certain amount on your state return (each state has its own thresholds regarding estimated taxes). You can use the vouchers or not use them, as you wish. For most people, if their income is earned on a W2 and the proper amount of taxes are being withheld, then they don't need to make estimated payments (unless they have other income sources which aren't withholding taxes).
Whether to make estimated payments is a decision for each taxpayer. If you make them, it cuts down on your tax bill at the end of the year. If you don't make them, and you wind up owing enough money to trigger the estimated payment requirements, then your state can assess a penalty on next year's tax return (at the federal level, the penalty is small relative to other penalties).
This is not something to sweat over, unless you're self-employed (since self-employed folks don't have a W2 with taxes withheld on their S/E income) or expect to have income from other sources besides your job. However, I would encourage you to check out your state's Dept of Revenue web site to see what its specific thresholds & penalties are, pertaining to estimated taxes.
