Not everyone has the time, tools, resources, or inclination to keep an aging vehicle from its ultimate demise.
And for the original owner, it's not economically feasible.
It comes down to the exponential wear and tear of a vehicle as it ages.
When new, oil changes got you through.
A bit later, oil changes, brakes, filters, and maybe tires.
Later on, tuneup, fluid changes, brakes, filters, tires, and lesser components.
Then major components, a myriad of smaller stuff, (hoses, bearings, bushings, shocks)...along with the usual oil changes, brakes, filters, and maybe tires.
All the while, said vehicle is worth a small fraction of its new-car cost.
Eventually, a typical owner will tire of this and cut his/her losses.
For us, we look at is a cheap driver that needs "a few items" to make it perfect. The PO sees the same vehicle as an expensive purchase that just keeps sucking money and continually loses value.
But the same can be said for electronic equipment, which may even have a steeper depreciation curve (especially PCs).
The salvage market is lucrative, and I too, can unearth a lot of goodies by taking the time to "scrounge around".