When my son started Cub Scouts, I went to a "University of Scouting" event. One of the classes was Merit Badge Counselor training. I signed up for it. The first thing they did was to have everyone introduce themselves, and everyone went around and gave their name and what troop they were with. They also talked about merit badge experiences in their troop.
When they got to me, I told them I wasn't with any troop, and that I planned to sign up as a counselor for the whole district or council. For most of the people in the room, that was the first they had ever heard of such a thing. They didn't think it was a bad idea--they had just never considered the possibility.
After I took the class, I found the application buried on the council's website, and sent it in. I never did hear back one way or another. I had volunteered for about 10 different merit badges, but I stated that I didn't want to do all of them, and asked them to assign me to one or two of my preferred ones, and if they needed me for the others, that they could use me for them as well.
I never was told which merit badges I was approved for, but a few months later, I got an e-mail from a local scouter who runs merit badge programs asking whether I could counsel one of them at one of his programs. That was the first I knew that I was approved. So I knew I was approved for that one (one of my optional listings), but had no idea which other ones I was approved for. Eventually, at Roundtable, they made an announcement that they needed to update The List, and we should confirm that we still wanted to be on it. I wasn't allowed to see The List, but they did finally tell me which merit badges I was approved for.
Today, one of the district's leaders is in our troop, and he has access to The List, and I've been able to confirm that my information is correct. But The List is still regarded as a mostly secret document. As far as I know, scoutmasters have no access to it. So if Johnny Scout wants to do X merit badge, I don't really know what they're supposed to do. I guess they need to call someone at the district who has access to The List.
Unfortunately, that issue never comes up, because I don't think Johnny Scout has ever been told that he can do any merit badge that he wants, just by making a phone call. I guess it's best that he doesn't know, since The List is such a closely guarded secret.
Anyway, now that I'm an approved counselor, I sit by the phone waiting for scouts to call. So far, that has never happened. I asked other adults in my troop who are counselors, and most of them have never gotten a call either. The one exception is a leader who counsels Environmental Science. He apparently gets occasional calls from scouts in other troops who got a "partial" at summer camp and need to complete it.
So I would say that a 20 page out of date typewritten list would actually be an improvement in my district. (Or maybe in my council--I'm still unclear on whether The List is a secret district document or a secret council document.)
So far, the only merit badges I've done have been where I put myself forward as a volunteer. Those have been at district merit badge events and a local scouting museum. Fortunately, two of the merit badges I counsel happen to be among the rare ones that work fairly well as a "class," where all or most of the requirements can be completed in one day (those are Radio and Signs Signals & Codes). Other merit badges I counsel don't really work very well as part of a "class," and I've declined requests to "teach" those classes.
I'm doing my best to get the word out that scouts can do any merit badge, and many of them work best when the scout makes contact with a counselor from outside their own troop. But I have to concede that it's not really done that way any more.
I suspect that there are a lot of people in the community who would love to be merit badge counselors and be able to share expertise from their job or hobby. Before my son started Cub Scouts, I would have gladly volunteered if someone had asked me, but they never did. Many of those people are former scouts, but there are probably a lot of people not connected with scouting who would be willing to help. But nobody asks them, and if they are asked, their name is placed on a secret list that nobody's ever going to look at.