Why would their way of handling memory for conversations have much to do with how they will analyse your user profile for ads? They have access to all your history either way and can use that to figure out what products to recommend, or ads to display, no?

It's about weaving the ads into the LLM responses overly and more subtly.

There's the ads that come before the movie and then the ads that are part of the dialog, involved in the action, and so on. Apple features heavily in movies and TV series when people are using a computer, for example. There's payments for car models to be the one that's driven in chase scenes. There's even payments for characters to present the struggles that form core pain points that that specific products are category leaders to solve.