The only reason it didn't happen sooner was because SMS prices were nuts ($0.20 a text at one point![1])
That all changed with the advent of data plans and non-sms messaging services. Once those two things came together there was no way for a telcom to keep charging through the nose.
With spam callers ringing off the hook now, it's no wonder why everyone just texts now-a-days. All my calls go straight to the google answering service if they are from unknown numbers. In the past year, maybe 10 of them have been legitimate (out of literally 100s!).