Gifts are never seen as having been produced, they are always merely transfered as assets. The only thing that happens with the granting of a gift is a transfer of ownership.
In a market economy the measurement of transactions is a proxy for the measure of what is produced and consumed. Gifts don't show up in that metric. They do not appear as market transactions, and so they do not register as product.
The gift of life, of child care, of household management – all these things are gifts and so do not register as part of the national product. The misleading implication is that nothing is being produced when things are given away. Product, in market economies, is measured only in terms of the cost, not the benefit. All that is happening with gift exchange is that things are being moved around in the domain after consumption has already occurred so it is just a matter of who ends up with what, not how much is being produced/consumed.