The problem is the deps: You can have Rust with no nulls, but the OS was made by it. You can have a RDBMS with ACID, but the file system is liar.

Then, you can make a product that was applied engineering, but you can't replace all the others that not.

Civil engineering and friends have the advantage that is built on top of the universe, that despite claims to the contrary, was not hacked with perl!

Engineers also have this problem: if the transistor doesn't meet its claimed tolerances then the robot won't either.