If it may be a helpful perspective - I don't care if I phone one's room phone or cell phone; but texting/messaging is a completely different mode of communication than a phone call to begin with.
Texting, like messaging and email, are async whereas phone is sync. For 99% of my communication, I don't need to talk to somebody right now (and they don't need to talk to me right now :). I don't care if other party has a cell phone or not, but written comms is preferred to voice comm for large number of my requirements.
Similarly, email/messaging/text can trivially be a group conversation, and plans can be narrowed down or many people can be informed quickly; again, don't care if other party has cell phone or not, but in many circumstances I'd prefer to send one quick message/email/text, than to call 7 people.
(lest you think I lack empathy, I am of course on the other side of the equation too! My family is all on Whatsapp, which for me is the worst messaging system that an evil mind could possibly invent, so I feel the pressure :)