Studies show that people who use devices within two hours of going to sleep are more likely to have sleeping problems/disorders. Using a device before you go to bed will decrease melatonin levels which will make falling asleep more difficult. The screens trick your brain into thinking it is day which in turn makes you less tired. The side effects of using devices before you go to sleep aren't worth the tiredness and loss of motivation for the next day.
i dont think parents should do this, they should trust their children to be responsible and not go on their phones, some children arent very good at waking up and they need to set an alarm, some people like to have their phone by the side of their bed because they might feel safe knowing they have their phone their in an emergancy, or they like to charge their phone.... its not like they can put their phone on vibrate or mute so i dont see the issue is this.