I think it's symbolic of a lot of things - namely not letting the bad guys win, carrying on as normal as possible in the face of terrorism, getting back to some semblance of normalcy, etc., not to mention giving people under incredible stress a little stress relief from an old fashioned ballgame. (During the Boston Marathon bombings the Red Sox played a big part in the healing of the city.) It also no doubt brings a lot of revenue into the city, as well as pride and joy, etc. I don't think it's so out of place.
Turn on any news station and it's part of the headlines as well.