The primary motivation for rolling out the cell networks was to provide voice coverage, or else SMS wouldn't be a hack on to the GSM protocol and we won't have

The primary motivation for rolling out the cell networks was to provide voice coverage, or else SMS wouldn't be a hack on to the GSM protocol and we won't have things like a 140 character limit. Before there was voice, there was paging. I'm not super familiar with GSM, but I know for CDMA the reason SMS messages have a small fixed size is they used to go out over the paging channel. I don't think that's the case any more for CDMA. I'm kind of surprised it is for GSM. In any case, the point is there's no objective way to untangle costs in an item that has a large implementation cost but provides more than one service.