Just click below to visit Alter Aeon's voting links page, where you can vote for Alter Aeon at any or all of the sites provided.
When you vote for Alter Aeon, you're contributing to an informal poll of game players to shout out to the world, "Hey, I like this game!"
The voting sites may take steps to make the counting and voting more fair, but it's not a scientific process. Nevertheless, the results are used to promote whether a game remains popular or whether its user base has waned. This in turn helps other players find the good games and avoid the sleepers.
The most logical reasons are cost and benefit. It costs nothing to play, and nothing to vote. The benefit is that it helps the game keep running for free. The game has been free for more than a quarter century, and is likely to stay running as enough people keep playing. But an additional benefit is that voting doesn't just keep people playing, it also helps advertise the game to new players, which means additional people for you to interact with in your adventures. (Yes, you can consider the time-is-money factor in that time spent voting is a sort of cost. Except that cost of that time is minimal compared to any time spent playing, and one can eliminate that simply by multitasking and voting while playing, perhaps while your character is sleeping after a battle.)
Logic aside, it's just a nice way to say "thank you" to the game administrators for making the online world that we enjoy.