For Airplane mode, if you try to use data or make a call, users are alerted immediately and a button prompts to disabled it.
There is no prompt for DND, and often users have it on mistakenly, meaning they are missing calls and texts unknowingly, resulting in a poor user experience.
As shown in this thread, we have seen that this setting is enabled on many iPhones by mistake, which means Apple should look into it. Apple should poll their retail stores and ask how many Genius' come across this same problem - I bet the numbers are high.