Like a number of others, I can't set my phone to DND overnight - I need to be able to answer calls if it's an emergency. I also need to be able to answer texts in an emergency. And no, I can't set it up to have only certain numbers come through, because often the emergency call will be from a hospital or similarly number withheld number.
Given that I'm likely to be disturbed for genuine emergency calls, and given that I have to assume any call or text at that time is an emergency, so must be read immediately, yes, I get a little tetchy when people text me for no good reason at silly o'clock in the morning.
Thankfully, I have decent friends, and once I point this out to them, they usually stop. I have had to ask one particular friend to please try to remember I go to bed significantly earlier than she does though.
If I want to leave a message rather than get an instant response I'll either email or more likely Facebook message someone - it'll still be there ready to be picked up when they next look st their phone, but won't ping ping through an emergency.