The Locomobile type steam engine was ideal for a variety of industrial applications. It was a simple twin, so would not stick on dead center, and were a self-contained unit with reverse gear. This made them ideally suited for many applications such as driving conveyors, stokers, hoists, and feeding sawmill carriages. By way of comparison, take a look at the Soule' Steam Feed Works "Speed D Twin" engine. It is a bit heavier than the Locomobile, but was specifically made for feeding sawmill carriages.
My guess is the Locomobile engines were too good to throw in the scrap heap and were something most mechanics and mill owners understood and could see another use for. "Standard Stoker" made a fully enclosed simple twin steam engine. It was intially developed to drive auger feed stokers on steam locomotives. The Standard Stoker engines wound up being ordered and installed on Skinner Marine Steam engines as "jacking engines". They turned up in other applications once the railroads got rid of the steam locomotives. In one wierd twist of fate, I saw a "Standard Stoker Engine" being used as a winch in a locomotive shop. It was mounted to a column, and run on compressed air. As a winch, it was used to pull dead locomotives into the shop. Maybe it might have been used for pulling steam locomotives for valve setting, but when I saw it, it was pulling in dead diesel locomotives. A small simple twin steam engine with reverse motion is something that is readily applied to many applications. The Locomobile engines were light in weight, so could be easily mounted in some new application. A "Standard Stoker" engine or a "Speed D Twin" engine is probably nearer a half a ton in weight, while a Locomobile engine looks like something a man could pick up and carry, sized for a light "buggy" type vehicle.
As a parallel to the comment about the CUmmins diesels vs surviving Dodge trucks; the Model T engine was one engine that saw a lot of re-use powering a lot of things other than vehicles. I have no idea of the statistics as how many Model T's were made vs how many engines outlived the cars as power units. In years past, people took old truck engines and used them as "power units" more frequently than nowadays. A local sawmill near me had been powered for years with the engine from wrecked Mercedes truck. The "power unit" consisted of the engine, bell housing and transmission, still on the frame rails with the radiator. The truck's driveshaft was modified and coupled to the drive shaft of the sawmill. It was quite common a few years back to see the radiator shell of some old truck and the engine and transmission powering something else. I've seen an old Mack radiator shell and diesel engine grafted into a Northwestern crane, and a number of other old truck engines grafted into sawmills. With the move to hydraulic excavators and band saw mills with hydraulic feed, it seems like very few people are grafting truck engines into heavy equipment or sawmills.
The Locomobile engines were well built, a versatile design, and light enough to be lugged off and re-mounted somewhere else without too much effort. Re-applying a diesel truck engine is a lot more work, and today's equipment does not lend itself to this sort of adaptation. My guess is today's diesel truck engine will wind up as scrap, replaced by more fuel efficient engines or more emissions-compliant engines, or else remanufactured for re-installation in trucks.