If dynamic array bounds checking cost 5% (narrator: it is far less than that), and we turned it on everywhere, we could have computers that are just a mere 950X faster.
If you went back in time to 1980 and offered the following choice:
I'll give you a computer that runs 950X faster and doesn't have a huge class of memory safety vulnerabilities, and you can debug your programs orders of magnitude more easily, or you can have a computer that runs 1000X faster and software will be just as buggy, or worse, and debugging will be even more of a nightmare.
People would have their minds blown at 950X. You wouldn't even have to offer 1000X. But guess what we chose...
Personally I think the 1000Xers kinda ruined things for the rest of us.