To quote yourself, that’s a bullshit cop out response.Big whoop. Without comparing it to other user groups it's meaningless.
The work they do is absolutely not meaningless. There are trails across the Northern Rockies that would be pretty much impassable without volunteer work by Backcountry Horseman. Given a fair portion of it is within designated wilderness, it serves no benefit to the MTB crowd, so there is context in everything.
I’m sure the local bike club could care less about a boardwalk through a wetland in the Bob Marshall, but it’s still valuable work.