I guess it all depends on who you are. Some international carriers I've worked with, handling SMSs is a net loss to them - but they have to do it(as a side offer to gain customers for services they do make money on, mostly voice traffic, and because they're lawfully bound to do it as they're operating a country's international SS7 border gateway).
Also, telco equipment isn't cheap. All those tens of thousands radio towers, exchanges, cables cost arms and legs. They have to make that money somewhere. Though, I've no doubt someone's getting far richer on your SMSs than what would be sensible. Entering this market is a huge barrier - you need expensive equipment, you need licenses, you need interconnection arrangement with other carriers, and you often need to build up a physical network. Thus, few actors and little competition.
Here's btw. a screenshot decoded SMS message captured on a SS7 network for your pleasure :-)
http://imgur.com/E0qKv
Also, telco equipment isn't cheap. All those tens of thousands radio towers, exchanges, cables cost arms and legs. They have to make that money somewhere. Though, I've no doubt someone's getting far richer on your SMSs than what would be sensible. Entering this market is a huge barrier - you need expensive equipment, you need licenses, you need interconnection arrangement with other carriers, and you often need to build up a physical network. Thus, few actors and little competition.
Here's btw. a screenshot decoded SMS message captured on a SS7 network for your pleasure :-) http://imgur.com/E0qKv