I'm sure it varies wildly by the type of program, and I'm sure much smarter people than me on the Rust team did their benchmarking homework when they originally made the choice. Just saying that to me, it seems like a reasonable default
It seems like a seriously wrong default for a language whose story is supposed to be safety. People wanting unsafe languages already have C and C++ for that :/.
To improve safety at large, Rust has to displace C++. People use C++ in part because of its speed (rightly or wrongly - but it is undeniably part of C++ culture). A language which is consistently slower than C++ will not displace C++. So, this was a point where the designers decided to hold their nose for now.
