You're missing the point if you argue that any backup could be stolen whether it's on a titanium plate or a piece of paper. That's not the point. The point is that it's better if your backup can stand the test of time and other external factors or loss vectors. There are many loss vectors that should be taken into account, not just stealing or negligence or laziness or whatever.
All things can be lost or damaged or destroyed physically or digitally and because of many risks. It's the same for wallet back up methods that are all damageable but different methods will have different levels of security and survival against damaging threats.
Paper is vulnerable with many threats like water, fire, acid and more, metal/ titanium plates are better against these threats but there are catastrophes that can destroy all including wallet backups like massive powerful explosions from bombs, nuclear bombs, earthquakes, tsunamis. When these catastrophes come, we have bigger priority than wallets and need to keep ourselves alive first.
The reason why there's innovation in seed storage devices is to make sure your backup lasts despite a number of negating factors.
With available different back up methods, we can use some of them for our wallet backups. By making different backups with different methods, and storing these backups at different locations, we have better preparations against unwanted events and increase chance to always have accessible and usable backups.