Look at it as if it's using unused parts of the signal spectrum to fit in another signal instead. Sometimes less error resilience in exchange for more data is a worth while trade, see for instance 256-QAM compared to 4-QAM (although not quite the same, I admit).

I get what you mean, it's a misuse of the underlying technology and a crude hack in some ways, but if it's stupid and it works it's not stupid.