It's not so easy for them to integrate ads. I happily use LLMs to help me find the best product. As long as it really delivers on that. If I realize the results are manipulated by ads, i'll stop using it. Or I'll switch to a competitor LLM which does a better job. It would be a problem, if we had only one player in the market. But there are a few. And they need to be careful to not skrew their reputation. LLMs have a fundamental aspect baked into them. Namely the final goal of giving you "the truth" about a subject. This is an inherent problem for ads or any other kind of manipulation.

How are Chatbot UIs different from search engines? Just look how that turned out... Yeah we have Kagi and DDG, but quality, completeness of results (for most topics) and cost still drives most people to Google.

Switching is maybe feasible for those who have the resources, but the majority will be stuck with large providers. They establish quasi-monopolies, then monetize (with ads). It's the sad cycle of commerce.