...was a really bad idea. SMS dates from 1984 and was originally a hack -- a beautiful hack, yes, but still a hack -- to squeeze basic text into empty 128-byte slots in telco switching protocol SS7. Combining multiple SMSes together requires nasty User Data Header hackery, and transmitting binary data over this joke of a channel is even worse. And don't get me started on MMS, a horribly overcomplicated spec that neither handsets nor operators could ever implement correctly, much less interoperably.
I used to work on this stuff for a living, and ran away screaming as soon as I could. The mobile messaging world would be a good ten years ahead of where we are today if we'd copied Japan in the mid-1990s and ditched SMS/MMS entirely for email built on packet-switched data, which would have instantly created the decent infrastructure needed for future apps. (The packet-switched bit, that is, not SMTP itself.) But as always, Japan shot itself in both feet by refusing to adopt the same standards as the rest of the world, meaning that e-mail and decent Internet on phones didn't become a mass-market thing elsewhere until the iPhone came out in 2007.