Because 300 years ago, the Kingdom does not provide incentives to its citizens and employees (no healthcare to the majority of citizens, the security sucks, etc.). We can all agree that taxes are running the government now, without it the "system" would probably collapse, along with the country as a whole.
Healthcare is covered by healthcare tax. I'm talking about income tax.
It would have to cut spending but it wouldn't collapse. Back in the Roman days being an MP was an honour. They weren't getting crazy wages 3 times higher than average citizen. A US senator gets $174,000 a year. That's 14,5 k a month while you're working your ass off in a corporation to get $2k. 5k a month is already a very good wage and those leeches are getting raises! They used to get 150k a year but that wasn't enough, now they're getting 174. It's the same everywhere.
In the EU MPs are getting €8k a month! In most parts of the eu the average is 2k and if you're getting 3k you're considered wealthy. They are getting 8, because their hard work of rising their hand and speaking their mind once in a while is worth more than that of a surgeon or a pilot.
Another thing, the government tax that much because back then the labor, the employment, the businesses aren't as prosperous as the present. And I should also include that, Fiat money is getting worse and worse in exchange for whatever it's worth for products and services.
They can say that they can tax the "rich people" but still gets away with it.
The work of a man was always paid accordingly and you might think the businesses weren't big back then because there was no industry and everything was being built by hand, but people had nice businesses, but making simple things like candles, wine, furnaces, bells. It doesn't matter how big their companies were they were always paid for their time.