I am generous and give my time freely.

A tenner can be earned back. Saturday morning cannot. That difference goes unmentioned whenever the two get spoken of as the same kind of giving.

It is also why an hour lands so much harder on the person receiving it. They know precisely what it cost, because they have the same twenty-four as you and no way of manufacturing more.

Somebody who gives up a Saturday to repaint your kitchen has said something no cheque says. It does not scale, it produces no receipt, and it gets remembered for decades.