[cmonreally123]

Because if they did the 9$ ads would plummet in price paid to the platform because it implies to the advertisers the consumers have no purchasing capability and may be price sensitive or else they would shell out the extra dollar. If they don't offer it and still sell adds they can demand advertisers pay the premium as the consumer has disposable income to buy the service and is likely price insensitive since they are now paying for something that was free.

[Analemma_]

Is this actually true? It's one of those bits of "telephone wisdom" I've heard passed from commenter to commenter on Hacker News (and Slashdot before that) for as long as I can remember, but nobody ever seems to have a primary source for it, it's always been a "just trust me" bit of knowledge.

[otabdeveloper4]

It isn't true. Advertisers think in broad social groups. ("25-44 women with kids", "men with college education", etc.)