If they didn't tax your savings, pay, car, fuel, house etc etc etc etc etc they would directly tax you 100 times more than they do now.
The question should be why do they waste so much..
At one point (a few years back) 68% of the population of the UK was paid directly or indirectly by the government. NHS, police, fire, armed services, goverment both local and national as well as all the scroungers. On top of that all the contractors and suppliers to these.
That's why they need to tax us so much.