'once-used-never-sharpened' - Explained
1) Rental company rents saw to inexperienced user (does not have own saw), who promptly drives the chain into the dirt, then complains that he was given a dull chain. By placing a new chain on each rental, and showing this to the user, this complaint is less likely to happen. Rental company builds the price of a new chain into each saw rental.
2) Busy, for profit company calculates the cost (including overhead) of their paid employees sharpening chain versus earning income and decides that it is cheaper to buy new chains than to spend time sharpening.
3) Sawyer who wants to cut, but does not want to sharpen. Unhappy with the quality of local sharpening service (say, at $7 per chain). Buys $20 loops in quantity, and gets 20% discount (pays $16 per loop). Uses chains once, then replaces. Sells used chains on Craig'sList or eBay for $12 each (40% off new, retail price). Net price is $4 per use ($16 - $12), versus $7 to get sharpened.
Could be a good deal for the right buyer and seller.
Philbert