Degrading your product by filling it with ads or, God forbid, by making the LLM returns less accurate and influenced by advertisers, makes ZERO sense for any LLM company due to the ubiquity of LLMs. LLMs aren't something special that no one else can create and use. Google is a poor example because it had a monopoly on search for a long time due to its foothold and technology, but OpenAI has nothing like that at all. OpenAI has no moat or "secret sauce" that would enable it to be more successful than any other LLM company.

If I can use an open source highly effective LLM locally, and have it do all of the things ChatGPT can do (and more), then what motivation do I have to use ChatGPT? The only motivation people would have is ease of use but if one service becomes bogged down and compromised then people will just shift to one of the other hundred equally effective services with less ads. LLMs aren't hard to spin up and put out there for people to use.

Honestly, I don't think OpenAI is going to survive very long unless they get incredibly lucky or they come out with some banger of a new model or new app but even then, IDK...