On your opinion, should it be necessary for everyone to teach Aikido in order to make their own progress?
The short answer is no. A person has to give back to the art is how I understand it. Teaching is a great way to give back but it doesn't mean one has to open a school. It could be just taking a class when your sensei is out of town or helping new students with their acclimation to class. Giving back could also be helping with fund raisers and daily dojo maintenance, record keeping, demonstrations and so on.
There are a multitude of ways a student can give back to the art.