“Modifying things in place” is, from the logical standpoint, an unnatural and even dangerous thing. A person that is not familiar with (imperative) programming often has a hard time understanding variables and assignments (similar to some programmers not understanding pointers). Mathematics doesn’t have assignments, either. That should tell you something...
It mostly tells me that mathematics does not care about runtime or space performance. Which is fine, because mathematics is about solving abstract problems, not getting a Turing machine to solve concrete problems.
