They want an oil that meets a certain price point. Unlike mainstream oils, which meet a performance spec of API, ACEA, or all the manufacturers for oils like 5w-20, HDEOs, etc. This pleases the folks who just dont care. $1.14 is half the price of a quart of havoline. Most don't know what oil they need, so they just scan the shelves. Either they see a brand theyre familiar with, or they see a super cheap bottle, and make a decision.
Theyre in the process of trying to please the customer. Theyre not in the in the business of looking out for peoples' warranties, theyre not looking out for the best protection of peoples' engines, all theyre looking for is a range or prices and quality levels on the shelf to please all customers.
Sure, SF might be A-OK per the spec for a late 70's early 80's vehicle.... but wouldnt they benefit from better additive packages and baseoils too??? Of course if they are on their way to the junkyard, it might not matter - but theysure have a lot of that SF stuff to just get the clunkers to drive to the junkyard.
JMH