We gain the same benefit all commerce creates: somebody wants to buy, somebody else wants to sell, both those people make a deal, both those people have fulfill

We gain the same benefit all commerce creates: somebody wants to buy, somebody else wants to sell, both those people make a deal, both those people have fulfilled their wants. The seller is happy because they preferred cash to the stock, the buyer is happy because they believe they can sell the stock for more money later. What difference does it make if the buyer plans to sell in a second or a month?