But Bard will also analyze the private content of messages “to understand the context of your conversations, your tone, and your interests.” It will analyze the sentiment of your messages, “to tailor its responses to your mood and vibe.” And it will “analyze your message history with different contacts to understand your relationship dynamics… to personalize responses based on who you’re talking to.”
Same way they get as much info about you as they can, to “personalize ads”.