A market enables you to trade more easily. And trade enables you to exchange something you value less for something you value more. That's the value gained. If instead of making a series of barter exchanges like a chain of quests in an RPG game, you can simply sell stuff you produce for money, and buy stuff you want for money, you gain time. Of course markets have their pathologies like speculation, and, it seems to me, unfortunately cryptos are mostly speculation.