> Are you seriously suggesting consumers of Google Ads (entities, worth on average, a few thousand euros) will go to court against Google (an 800bn dollar company)?

No, Google will sue them if they don't pay and the amount is large enough. That's a fairly trivial process in most legal systems. If you do use the legal system, that is. If you don't, you need to pray that your contractual partner keeps their end of the bargain because you cannot enforce the contract.

> Consumer contracts are enforceable due to reputational concerns and goodwill, not the legal system.

That's wrong. It's easy to enforce a contract, it happens all the time.