Sure, earning money is nice, but consider this: you are just throwing 30-50% of your income away. When increase of 100% means 200% more effort, because you're throwing away 50%, you really start considering if the effort's worth it.

Also, at least where I live, we have our benefits capped. So I pay taxes proportionally to my income, but god forbid I get sick, get in accident, lose my job or have a child and take a child rearing leave - even though I've been paying full taxes >10 years, i get instant income cut by 50%. And don't get me started about pension - currently it's set at 75 years for males - and average lifespan is about 70...

So, to sum up, while earning more money, sure, is nice, but throwing the money you've earned fair and square down the drain to support society which will simply not support you is disheartening to say the least.