I had always thought that this was a feature in that you would avoid truncation and both parties would know how many SMS were sent/received. I had no idea that anyone concatenated these. It is a bit problematic for those in the US on plans that do not have unlimited SMS because it would present the illusion of over counting.
I’m sure somewhere, some of them do. But not a single person I know, including many people purchasing the least expensive MVNO plans from places like Wal-Mart, doesn’t have unlimited SMS. How many people do you know who still have to worry about going over their SMS quota?