Why did the Messenger, may God's prayers and peace be upon him, not accept charity while he accepted gifts?

The Messenger of Allah, peace and blessings be upon him, would accept gifts but not charity, which was forbidden for him and his family for several reasons. One of them is that charities are "the impurities of people," meant to purify their wealth and souls, and thus they are not befitting his noble status, nor the honor of prophethood and its high station. However, if his family were deprived of their right in the public treasury and were compelled to resort to charity, then it would be permissible for them.