Because "we tested competitor A's oil, and it didn't wear out the camshaft, while our new formula proved beyond any doubt that it didn't wear out the camshaft."
Doesn't sell a lot of oil.
A marginally representative test that provides real, visible scars, and welding sells oil...I know, I've bought lubes and additives off one armed bandit salesmen in the past (long distant past), but I did.
(Once had Wynns turn up with a timken, and ask for our best grease, to show how good their offering was...it was MDF press grease that we brought out, synthetic bases, packed with moly, graphite, and teflon - they cried foul, as they meant "best normal" grease")