Companies also lobby heavily for these tax laws. The laws may be directly responsible, but big companies share some blame as well.
Your 45% number is misleading on it's own. People don't pay income tax because they had so little income to tax in the first place.
No it wouldn't. Our current regulated lobby 'industry' is an attempt to control something that would happen ANYWAY if it was made illegal. Furthermore, lobbying is necessary and a core part of any democracy. You need to be able to petition your representative government for changes, regardless if you're a regular citizen, an activist, a business owner, or even a corporate entity.