'nother thing people are missing.
Consider what Joe Public sees when he looks at the gun racks in a store. Joe ain't a rifle loonie like most here, but just a semi-informed average citizen looking for a hunting rifle.
For not very much coin, with a lever action Joe Public gets what feels and looks like a complete rifle, iron sights to be sure, but complete.
For the same price he can get a bolt action, usually without sights, or if a complete scoped set up you get a rifle/scope combo conspicuously built cheap to meet a price point.
The fact that a great many lever actions end up wearing a similarly cheap scope is beside the point, the original purchase had been made.
I know because I followed this route, except that the scout scope set-up I have on order for my Marlin cost me more than the rifle did.
If sales of new lever actions are falling, the lever actions may be the victims of their own past success. I believe there is something like five million Winchester and three million Marlins .30-30 lever guns out there. Most get used once or twice a year if that, and consequently do not wear out.
My own Marlin 336 is 44 years old and still functions good as new. Lots of lever guns are like that, eight million mostly working examples still in circulation while the number of hunters nationally stays about level or even declines.
I believe .30-30 ammo will stay in wide circulation so long as it sells, as it apparently still does at present (contrary to those links posted, I can usually find .30-30 at least as commonly as .223 or .308).
If/when .30-30 usage does decline, I believe this will signal a fundamental change in the hunting demographic: A shift away from Joe Public and his low-cost hunting oppportunities towards more specialized rigs owned by those serious enough and with the means to spend on higher dollar trips/leases or the like. The way hunting seems to be going in very many places.
If or when we do lose Joe Public, it will not portend well for the future of hunting in this country.
Birdwatcher
