I cannot believe there is no demand
Well, if you look at it this way ....
On the consumer side, every man and his dog has a mobile phone. It would take an awful lot of marketing money to persuade the man on the street that using an extra tool beyond the built-in capabilities of their phone is worth his while.
Then beyond traditional SMS in the "over IP" world you've already got BBM, Apple iMessage, Watsapp, Twitter DMs,Skype,Snapchat, Facebook Messenger..... is there really any market share left for something else to text "over IP" ?
The amount operators charge their retail customers to send a text are not extortionate either (and indeed, most will bundle unlimited or a stupid amount of free texts on the contract). Thus there would be little demand on the money saving side.
As for businesses, well, they'll want a dedicated SMS service anyway that they can integrate into their IT systems for automation purposes.
Adopting your argument would mean you would be unable to call a mobile number on SIP as there is another system to do that called a mobile phone!
Well, for your average punter who gets minutes included on their contract, using their mobile phone may well be the more attractive option !
As mentioned, mobile termination on SIP is just another route on the voice termination rate sheet.
SIP is a system to call any phone, including mobiles, so it must be logical to be able to text that number.
Well, the point is that SIP is a voice termination protocol. A mobile number is just another route on the rate sheet.
There is the instant message page mode on SIP via the
method=MESSAGE extension, but that was designed to be used between SIP clients. You might find one or two providers out there whose gateways will convert this method to an SMS on your behalf on their servers. But on its on, SIP provides no direct SMS functionality. Its first and foremost a voice protocol.
my telephone line will SMS a mobile - perhaps your's won't?
Don't know, I'm in the above category of people that's perfectly happy to send people an SMS from my iPhone.
