There was an old closed ticket on this - https://connect.microsoft.com/VisualStudio/feedback/details/173440/std-vector-resize-should-take-a-const-reference - but I thought I'd try to push this again.
The original response was: "After some investigation, we concluded that the current behavior is in line with the requirements of C++ standard and we are not planning to change the implementation.".
From the <vector> header:
void resize(size_type _Newsize, _Ty _Val)
The standard says it should be
// 220.127.116.11, capacity:
void resize(size_type sz, const T& c);
I don't believe that it is truly inline with the standard, since the current version has the possibility of calling the copy-constructor of the stored data type.