> SMS is no longer optional, even if you want to get rid of it, typically service messages are only sent using SMS, not voice and people will simply assume that

> SMS is no longer optional, even if you want to get rid of it, typically service messages are only sent using SMS, not voice and people will simply assume that even if you didn't respond that you still read their SMS message saying they'll be an hour late. And they'll be wrong. And an hour late. I would argue that politeness requires the sender to contact the receiver in a manner of the receiver's choosing, not the sender's, while the receiver should not go to extremes to avoid the sender. Lack of SMS is the normal, passive state and since there is no legal or social requirement to have it, I wouldn't consider not having it impolite at all. Odd, perhaps, if one takes the receiver's demographic into account, but not impolite.