Is your premise that when two parties trade, the selling party "wins" and the buying party "loses"? Ignoring the specifics of McDonald's, in general, the reason

Is your premise that when two parties trade, the selling party "wins" and the buying party "loses"? Ignoring the specifics of McDonald's, in general, the reason to make a trade is that both parties believe they will be better off. By not trading, it hurts both parties.