Because they don't realize the productivity of the capital is also taxed, and is taxed at the same rate as labour? That double taxation should sum to more than

Because they don't realize the productivity of the capital is also taxed, and is taxed at the same rate as labour? That double taxation should sum to more than a labourer would be on the hook for. After all, the value of capital is determined by its productivity potential. If there is no ability to generate productivity, the capital will be worthless, and then there will be no capital gains to speak of. Let's face it, the real problem with the tax code (in this country, but I understand the US is the same) is that the borrowed income against capital is not taxed at all. This allows one to effectively create money out of thin air without paying a cent.