[Sabramerican]

Capital gain income and ordinary dividend and interest income are economically indistinguishable.

What is indistinguishable is that no risk is taken to produce interest- possibly also dividend- income while risk is almost always present in producing capital gains.

[Torie]

The risk thing is compensated for seperately. You get a higher expected return (at least for non diversifiable risk). There is no reason to add a tax sop as well. And bonds have risk too: default risk and interest rate fluctuation risk (although treasury indexed inflation bonds have none of the former, and less of the latter).

[Sabramerican]

indistinguishable=distinguishable