It's pretty annoying, but then again I do it to some people but only to people I don't really talk to or know. When my friends do it I get irritated

and I was supposed to meet up with this particular guy twice - the day before we were supposed to meet he suddenly ignores my texts and doesn't show up

then he texts me like it never happened... UGH
But yeah like that user said when people do it in deal life, it's utterly disrespectful.