Why would it only be about one side? Why is it NOT about the reveiver getting something for free? Why do I have to pay income tax on money I earned by working a

Why would it only be about one side? Why is it NOT about the reveiver getting something for free? Why do I have to pay income tax on money I earned by working all year? I agree it is morally more complicated on the giver side, but on the taker side it is fairly clear cut. On the other hand the giver is dead and why should he have any more rights?