I'm a retired SM and I have some very strong feelings about this issue.
The bottom line is if the unit isn’t getting outside, the troop will die.
The troop I was associated with had been around for 40 years when my oldest son and I started with them. At that point they had a very outdoor activity oriented SM, who was preceded by a not so outdoor activity oriented SM. During the year or so before when the troop was not so outdoor activity oriented, the unit lost about a dozen boys.
When the outdoor activity oriented SM began his tenure, he cautioned that he intended the unit to be out side doing something every month. We – and five other families - joined the troop about three months into his tenure because they were active.
I took over two years later and continued that tradition. Both of us had annual and semi-annual planning meetings where the Scouts brain stormed what they wanted to do, followed by a parents meeting where we (only sometimes) brought in a dose of reality. Starting with my predecessor, the troop went for nearly eight years (I was SM for 6 years) with backpacking, camping, or paddling trips every month, and sometimes even more often.
Both of us emphasized backpacking more than just car camping and during that time we averaged about 25 active Scouts with another 10 – 15 less active to inactive registered boys. The Scouts frequently wanted to return to hikes and spots they’d gone to before and we would occasionally let them, but more often than not we would encourage new hikes in the same region. We tried to rotate the trips by both distance from home, distance for the hike (some were car camping in wilderness areas, to some as long as ten miles in), and terrain (forest, desert, mountainous, or beach – ocean, Colorado River, or Lake Mead/Lake Mojave).
Being from we hiked within about a 300 mile radius, with the majority of trips being either to the southern Sierras (averaging about 150 miles round trip for driving). The best year I had was one when the troop got weathered out (rain, snow, and oppressive heat for the location) four times during the year. The Scouts insisted we find another trip on short notice and they stuck with their planned outings for the year (that year it was twelve troop activities, Fall and Spring Camporees and Summer Camp).
After I retired and moved away, the new SM was a more not so outdoor activity oriented guy. The first year, he stuck with the monthly pace, but starting the second year he actually discouraged hikes because it didn’t fit his vacation schedule. By the third year there were less than ten Scouts actively involved with the troop. That was when he declared there wasn’t enough interest to go backpacking (he had three active ASM’s). The fourth year, after more than fifty years, the troop folded.
It’s an old saying, put the outing in Scouting, but it is a key element for any troop.