The answer is money. Selig's job is to run Major League Baseball, keep the owners happy, manage the players union, and put the best product forward so the owners make money.
Well -- the value of most Major League teams have been skyrocketing, fueled by a successful MLB lobby to get new stadiums. Players are making money, owners are minting money, baseball is still popular and relevant, and MLB has been introducing new revenue streams through the Internet. There's not another major sport that sells it's product on the web better than baseball.