paying less taxes doesn't imply that the gov't ceases to exist. The gov't has no competition, so every entity within the gov't has every incentive to increase their own revenue by maximally expending tax dollars.
It is up to the people paying taxes to reduce it, as a counter-balancing force, and hold the spending efficiency to a good standard.
It’s a revenue stream for governments, sure, but how much revenue a government needs is determined by what policies a government has in place, their obligations to pay employees and officers, and what additional services the government offers. The politics is all around that stuff, but a tax is still a taking of the money that someone else earned to pay for all that, including to pay public employees.
That’s also irrelevant because that doesn’t address what a tax is, or how it ended up in a government’s treasury, or why it is there in the first place.