Additionally what happens when the keys and person separate? Some scammer gets your key off of your computer and sells the title to themselves? Or someone loses the computer on which they had their title, and now can't sell because they can prove that they are them?
The real world is messy. And for most of the messy cases that the world has to deal with, the blockchain makes things worse. Not better.
For example consider title on property. Just putting it on the blockchain would run into trouble when you try to implement squatters rights https://propertyclub.nyc/article/squatters-rights-in-califor..., or the government takes the title back with eminent domain https://ij.org/issues/private-property/eminent-domain/califo..., or you fail to pay taxes https://www.sco.ca.gov/ardtax_public_auction.html, or the bank forecloses https://www.nolo.com/legal-encyclopedia/california-foreclosu....
Additionally what happens when the keys and person separate? Some scammer gets your key off of your computer and sells the title to themselves? Or someone loses the computer on which they had their title, and now can't sell because they can prove that they are them?
The real world is messy. And for most of the messy cases that the world has to deal with, the blockchain makes things worse. Not better.