Health:
You don’t know who is and isn’t trained. So what you are saying is not to put one in unless there’s a guarantee that a trained person is always there?
Take this hypothetical situation: What happens if during a bar mitzvah, for example, someone needs the AED, but it isn’t there because there were no “trained” people who were members. The person dies? Too bad, because in that large group of guests who showed up for the Bar Mitzvah were 5 hatzolah members.
The point is, you never know when it’s going to be needed, and who will be around at that time. It’s better to have it and not be able to use it, then to not have it when it’s needed.