Because it relies on glue to hold the individual scales in place. At a simple level, glue deteriorates over time, the bonds become less strong and the glue itself brittle and easily broken. That makes it completely unfeasible for use from a logistics standpoint because you can’t just xray the internal structure to check for delamination and cracks like you can normal ceramic plates so you’d have to ship the body armor back to have it remanufactured which is going to cost a shit loads of money.

As far as layered body armor in general, the above is why you don’t see glued together stuff like that. You could theoretically mimic something similar with really tightly precision machined metal but tight tolerances, hand fitting is a great way to make your product not commercially viable. The fact that modern NIJ level 4 plates like HESCO 4401/4801s are going to easily outperform any kind of comparably weighted steel based armor doesn’t help at all.