Yeah, because "free" trumps any paid service! They don't like it because they think WhatsApp / Telegram / iMessage are "free" - they ignore that connecting to these services is not free as they obviously still pay for the "data". Telecom providers have figured out they can more money by selling data than SMS or voice service. And that's why they deliberately price SMS or Voice service higher.

(Ofcourse, another factor is that SMS hasn't seen any feature upgrades. It's only recently that SMS has been upgraded to RCS. RCS has the potential to compete with WhatsApp / Telegram / iMessage etc.)