A phone conversation is understood to be free flowing. It's easier for us as humans to understand that someone is reasoning out a line of logic in real time over the phone. By contrast, a text is not real time, and should therefore be thought out before sending.
Fair enough, but that's only a reason to think out those text messages, not to avoid the medium. I occasionally keep drafts on my messaging apps for days, as I mull them over.
I'd say the same of email - lots of people just reply without really thinking. Especially nowadays that they are integrated into smartphones along with SMS and such.