"They" (meaning government actors) call it profit and demand a cut. The "profit" barely keeps up with inflation, if you're lucky. This is the lie of gov't, that it is profit. Gov't causes inflation that erodes the value of the dollar so it won't buy the same amount of goods over time, and takes a cut of "profits" so that the future increased amount of dollars can't buy the same amount of goods later on. Tax it when you earn it, tax it when you earn interest, tax it when you sell it, and tax it when you pass it on to your adult kids. (California now hiking property taxes on transferred property to adult kids). So yeah, not free of charge.