It doesn't work in real systems because it is extremely costly to the point of being infeasible. This has been known for decades and rejected because it doesn't

It doesn't work in real systems because it is extremely costly to the point of being infeasible. This has been known for decades and rejected because it doesn't actually work. If a technical solution is "obvious" and no one is using it, it tends to imply that it has serious flaws that are obvious to domain experts. Using encryption for deletion is known to be deeply flawed for unavoidable technical reasons. These databases actually exist. Almost no one uses them because the performance is exceptionally poor to the point of being nearly unusable for practical things.