פירוש על קידושין 99:14

The Talmud now explains why we need both mishnayot. Had we only the mishnah about kiddushin, I might have thought that a man cares about where he betroths a woman because in some places people like him and in others people do not. He does not want the agent to betroth her in a place where people might say bad things about him.
But when it comes to divorce, he would not care if people like him or not, therefore he might not care where the agent delivers the get. Thus we needed a mishnah to teach us that even with regard to gittin, if he says “give my wife a divorce in such and such a place” the get must be given in that particular place.