These days it seems even the humble school play is miked with radio mics and headsets. It is not only musical that is being radio miked,but a lot of the times it is just a humble play in a small venue. Have the audience lost their ability to hear? Are people getting lazy and using the easy way out? Why are more and more straight productions using the radio mic instead of getting the cast to project their voice. In the good old days performers could be heard over an orchestra, or if it was a straight play they could be heard easily at the back of the auditorium. It seems to me that performers are not being taught the basics of their craft, which is voice projection. I would have thought that this was one of the more important tools of a performers toolkit. Even in schools where drama, music etc is taught as a main subject there does not seem to be much emphasis on the concept of voice projection. Now if this is taught properly not only will you be heard but when you do use your voice there is less chance of you damaging it. There are plenty of people around who have done some pretty serious damage to their vocal chords because they have not been trained properly to use their voice. In fact there are cases of aerobic instructors who even with the assistance of a radio mic, still scream and have consequently damage their vocal chords beyond repair.
Now there are many factors that influence people to use a radio mic set up on their performers. The obvious one is that they are worried that the performer will not be heard. This is where vocal training is important. Now if there is not enough time for that, well a mic might be useful. The one thing that I have noticed when you mic up a performer who is quiet and has had no vocal training is that they seem to speak even quieter, as they believe the mic is going to take care of the volume factor. Well sorry folks but you still need to project when using a microphone. Projecting is going to make the audio guy really happy as he has less work to do.
The voice is a very important instrument and it does need to be taken care of. You do need to have your voice trained if you are going to use it effectively. If you teach drama, or direct etc you should make sure that your cast can use their voices effectively and without damaging it. In fact under the OHS regulations you may need to make sure that the voice of your performers are looked after and that sufficient training has been given to make sure that the voice is less likely to be damaged. You are asking a lot of your performers so you need to make sure that they are up to the task and have the necessary skills. So getting the voice trained is really important, no matter what age the performer. Directors, drama teachers etc need to devote some time to making sure that their performers are doing vocal exercises and looking after their voices.
So do you always need to use radio mics for shows, well in my mind no. Voice training first and then supplement the voice with a mic. The mic is not a substitute for bad voice training.