In game theoretic terms, there's no reason to assume repeated play, or that one day you will be on the opposite side of the table.

Stipulating your assertion--which I don't think is true in general--there's also the fact that people with whom you deal once can communicate with one another, leading to the concept of 'reputation', which is another kind of asset. A strict but enlightened portfolio-maximizer should prefer, under fairly general circumstances, a combination of money and positive reputation to somewhat more money but negative reputation.