Taxes seem to be applied to "income", in a broad sense: When you get money, it gets taxed. Why should it not be taxed just because you got it from your dead great-uncle, just for being his great-nephew, in stead of getting it from your employer, just for showing up and looking dumb forty hours a week? In both cases, you're getting money that wasn't yours before; in both cases, you're asked to pay part of it in tax. Perfectly logical and sensible.
Fuck, the only thing more logical and sensible would be to lump it all together -- the wages of work, capital gains of all kinds, inheritance, everything -- and tax the whole shebang at the same rate. Income is income; why should some of it be taxed much less than other kinds? Especially since in most economies, it seems that the kinds of income the well-off are more likely to have -- capital gains and inheritances -- are taxed less than the kinds the less-well-off are more likely to have (wages / salaries, basically). By pure coincidence, I'm suuure...
As for your "stealing" gobbledygook... Well, the less said about that, the better -- for you. (Though it's good to know, if you ever were to become unemployed, you have excellent fallback opportunities: As a spokesdrone for the RIAA, the MPAA, or some other gang^H^H^H^Hassociation of that ilk.)