"the whole point is to convince people to buy your product/service where, left alone, they wouldn't. " - your implication is cynical. Some of the time the reason you wouldn't is that you're ignorant of a better way. Certainly you don't want a better mousetrap if you don't know they exist. In that context, advertising and sales is just a way of getting the word out that something better is available.
I strongly disagree. My implication is down-to-Earth realistic, whereas your argument is a Motte-and-Bailey defense of the advertising industry. Yes, informing consumers about what's available on the market is crucial for good operation of the market. No, that's not what the advertisers do.
Informing consumers is putting yourself in Yellow Pages / catalogs of companies. Informing consumers is making a catalog of your products available. It's having a product page available with full specifications up front. It's showing up on trade shows.
Informing consumers does not require spamming them with e-mail and snail-mail, banners, billboards, leaflets or interstitials. Informing consumers does not require branding, or polluting every inch of space available to you with said branding. It does not require tracking people, spying on people, or manipulating people with dark UI patterns, dishonest journalism (aka. native advertising), paying people to lie to their audience (aka. influencers).
Most of money and effort in advertising is not spent on honestly informing people about availability of a better mousetrap.
