Do you sign in with a Microsoft account? If you do, that's probably the reason why you don't see ads in Windows 11. The system settings UI on Windows 11 always shows an ad which says that an account should be used to use office and other apps.

Microsoft has updated apps even on Windows 10 to recommend other apps. The Photos app was recommending a video editor app recently. Windows 11 shows ads, suggestions and installs a lot of garbage apps to upsell people into office 365, Onedrive and other things.

I recently had to reinstall my office that I bought. It signed me into an account without permission and uploaded documents there. I had to sign out of that account to prevent it from uploading documents automatically. Most of the documents I edit contain my PII. I can sue them.