If you apply your suggestion to existing x86 designs, you would get chips that are slower than current ones while needing more silicon for security features - s

If you apply your suggestion to existing x86 designs, you would get chips that are slower than current ones while needing more silicon for security features - so they would be slower and also more expensive just to mitigate some extremely-difficult-to-exploit vulnerabilities. I don't think anyone would actually buy those chips. Maybe they could be marketed for applications with higher security requirements, but that would make them a niche product and thus even more expensive. (also not an expert however)