If you’re on a computer and you get a text on your phone, wouldn’t it be great if you could reply without picking it up? Yes, it would, and there are great apps and services that enable just that ...
When you pick up your phone and type away, it's usually to check in on someone, share gossip you were supposed to keep secret, or ask for a favor. You rarely do it to send a simple "hi, how are you?", ...