We have several Cowboy churches in our general area. There's one not too far from us that we visit from time to time. They have services on Tuesday evening so they don't compete with Wed night Bible study at most "traditional" churches.
Amy, based on my experience with the one near us, these are just ordinary hard working God fearing people. Many are what some would classify as po folks. They feel comfortable driving their old beatup pickup truck to church. Feel comfortable that they don't need a 3 piece business suit and tie to worship the Lord. I'm sure that many of them never sat on a horse in their life.
And, the membership isn't just men. Some singles of both sexes and some families. All ages, from too young to sit on a horse to too old to do the same. Again, from what I've seen and heard, a better name for the one near me is an old-fashioned country church. Amens and praise the Lord are often heard from the congregation. Along with heartfelt prayers.
Don't write them off until you see and hear for yourself exactly what happens in a Cowboy Church, Biker's Church, or even an Outdoors church. Every congregation is different, I'm sure. So, in that regard, I can only speak for what I've seen and heard myself.
BTW, in closing, our church also has an Outdoor ministry. While it isn't a separate church, we do have events that focus on God's Great Outdoors. What's the difference between sponsoring a Vacation Bible School for children and sponsoring an event geared towards hunters and fishermen and their families?