Why are JIT-ed languages still slower and less memory efficient than native C/C++?

Some reasons for differences;

• JIT compilers mostly compile quickly and skip some optimizations that take longer to find.

• VM's often enforce safety and this slows execution. E.g. Array access is always bounds checked in .Net unless guaranteed within the correct range

• Using SSE (great for performance if applicable) is easy from C++ and hard from current VM's

• Performance gets more priority in C++ over other aspects when compared to VM's

• VM's often keep unused memory a while before returning to the OS seeming to 'use' more memory.

• Some VM's make objects of value types like int/ulong.. adding object memory overhead

• Some VM's auto-Align data structures a lot wasting memory (for performance gains)

• Some VM's implement a boolean as int (4 bytes), showing little focus on memoryconservation.