99% of the gain is about a very simple set of exercises. I maintain that most people would get a superb musculature with just cycling/running, squats, deadlifts and bench presses (ignoring pre-existing injuries). 4 exercises where the most complex machinery is a bike, and even that can be replaced with running. Doing it consistently is the key.

But then two problems happen:

1. People try to find shortcuts to make things easier. This is basic human nature. 2. While looking for ways of making it easier, a huge pile of salesmen insert themselves into people's attention, peddling the latest program, diet, fad, complex equipment (hello Peloton), etc. At that point, anyone who doesn't have >10 years of experience with their own body will simply be lost and unable to discern true good advice from drivel.

As pointed out before, there's no money to be made, no "value to be added" to 4 dead simple exercises with a one off expenditure. There's no subscription to be sold, nothing can be turned into a service if the equipment lasts several lifetimes. The weights you buy yourself can be passed down to your kids, and they will likely be able to pass it down to their kids. A hunk of chromed steel can last a very long time, the only thing you have to buy is maybe running shoes or gears for your bike.