Most people see text and voice calling as "ways to reach anyone at any time", and email/IM as "ways to reach people who are at computers". I think the people I know, at least, who compare texting disfavorably to calling, do so on the basis that "if you wish to reach me when I'm not in front of a computer, there are two ways to do it, and I would like you to do it using the one that does not irritate me / cost me money."