Ads are profitable because there is a large competition for attention. Once you have attention you can sell access to it. That's why influencers exist too. The

Ads are profitable because there is a large competition for attention. Once you have attention you can sell access to it. That's why influencers exist too. The alternative is selling yourself, but ads and paid promotion let's you garner attention unencumbered and make more. Social media companies also rely on the network effect heavily, it's an all or nothing proposition for them, if no one you know or care to know is on their service they are useless to you.