One of the reasons: if you want people to buy your next thing. (I was fairly highly ranked online in one of the Ace Combat fighter pilot franchise games, and had built a stable of planes in another one. But when they shut down the servers for the previous installment, after introducing a new one, I found I couldn't get interested in investing in the new one, if it was only going to get ripped out from under me like the previous.)
One of the reasons: if you want people to buy your next thing. (I was fairly highly ranked online in one of the Ace Combat fighter pilot franchise games, and had built a stable of planes in another one. But when they shut down the servers for the previous installment, after introducing a new one, I found I couldn't get interested in investing in the new one, if it was only going to get ripped out from under me like the previous.)