Carriers charging too much is exactly why WhatsApp became so popular in so many countries. It was optimised for very little data usage, so was dramatically cheaper than SMS.
Don't forget you could also send photos with it, which is more than what can be said about MMS.
Funny enough, I think I was charged once for a MMS in the past 5 years. No idea how I managed to do it, but it seems to still exist and still be charged per message even on my unlimited everything else plan.
