I'm actually fine with this because they have the courtesy to inform me (I can then make alternative plans). What annoys me, and I think what everyone meant before, is when they just don't show up and don't say anything, and usually don't answer their phone when you call.
Being decent humans, we would naturally wait a bit longer in case they are late, or perhaps something happened causing a delay. If they are not intending to come anyway, it just wastes our time, which is disrespectful.