Snapchat probably does not want to break all of their deployed-and-delivered apps. If they shipped the app/service without a "force the user to update" feature

Snapchat probably does not want to break all of their deployed-and-delivered apps. If they shipped the app/service without a "force the user to update" feature, they would risk leaving thousands of users in the dark. And if they did modify their protocol, it would probably get reverse-engineered again, either by the OP or somebody else.