Either way, iMessage comes by default, and every iPhone is guaranteed to have it. Using iMessage instead of say, Whatsapp means I don't have to download yet ano

Either way, iMessage comes by default, and every iPhone is guaranteed to have it. Using iMessage instead of say, Whatsapp means I don't have to download yet another app and sign up for yet another service and search for yet another user(not to mention possibly giving away personal information to Facebook) when I can already use what's already on my phone.