@Red - well then when you get out of university, I hope you live somewhere with a good public transit system or safe biking lanes and that you find a good playing employer there who acceptsthat you will be biking/riding a bus.
And bo is partially correct that the politicians who raised taxes to buy nothing but build up reserves would be run out of town. The government is not a for profit organization and it is accountable to the people. Building up a reserve may sound like a good idea to you (and many of us), but two things would happen: one, the people wouldn't reelect the officials who took their manoey to "bank it for a rainy day" and two, the money would get spent on pet projects despite. The government in general is not good at holding onto money. That's why when there is a surplus it generally goes back to the people in the form of a rebate/tax break.
One additional thing to note is that most taxes are earmarked for projects or specific funds. Recently the city I live in wanted to move just .1% (1/10th of 1%) out of the 1.5% it collects in payroll taxes into a different account with other purposes because the pupose it was originally earmarked for came in under budget and wasn't needing it but another did, so to avoid giving it back then having to pass a tax increase, they came to us voters and asked permission to redirect it. It was a smart move as it passed with more than 90% approval. Had they not done that, they would have had to give us a refund (not a bad thing), but then tried to pass a new tax which may or may not have gone through.
Not all tax money is slush fund money. The feds like to pretend it is, but local and state governments are held to a higher standard of accountability. Unlike you paycheck (if you get one), this is more like the money for your student loan. The people loan it for a purpose just as your student loan is for a purpose and it is fraudulent to use it for anything outside of that purpose.
Now, additionally, because the taxes are earmarked for projects,but because those projects can't usually wait, the governments take out loans. You might wonder "why can't they wait?" It's simple. Many circumstyances can cause them not to wait. PErhaps it is a new bridge because of some disaster befell the old one or perhaps a sports teamis threatening to leave town if they don't get a new stadium. Sometimes it is a matter of a growth explosion (a good thing) means that the infrastructure is suddenly insufficient. But one key aspect to the borrowing is that alomst always the lenders require proof of being able to pay it back, so they have to get the tax passed first for the project *then* they canborrow the money and pay it back over time. But the project cannot wait 5 or 10 years until the funds have come in from the tax.
When you own a house, even if you save for 10 years and buy an inexpensive one for cash, you will discover how things can creep up out of the blue that were never budgeted for and that no amount of savings planning could have compensated for. The government deals with this all the time, so they, like us, borrow money.