I find it very weird as well. So a store shouldn't show products it sell? Only allow them to be searched?

I understand being anti-add, but we are talking about store here selling and distributing products. Which makes reasonable attempt to serve relevant suggestions to user. Of new games or games that are somewhat based on what users have already played or followed.

Now if Steam store was showing third-party advertisements I would be on barricades.

And no one actually forces you to use the Steam on Steam Deck it is linux box with root access in place...