There are more details below, but even if you fall outside of the refund rules we’ve described, you can ask for a refund anyway and we’ll take a look. Valve will, upon request via, issue a refund for any reason, if the request is made within the required return period, and, in the case of games, if the title has been played for less than two hours.
Maybe your PC doesn't meet the hardware requirements maybe you bought a game by mistake maybe you played the title for an hour and just didn't like it. You can request a refund for nearly any purchase on Steam-for any reason.