My guess: for backwards compatibility. I bet you also still get that oh so useful "Windows made this file for you" text file if you use a traditional Windows solution template.

For those unfamiliar with this issue: if you include Windef.h (directly or indirectly) you get what the platform provides. That file by default defines min and max macros. To prevent that, define NOMINMAX before including the windows header (in the source, or as a command line argument to the compiler). (https://support.microsoft.com/en-us/kb/143208)

Compatibility for old code? Just "#define NOMINMAX" before including windows.h

In fact, VS's STL has to defend itself against those macros. Since the user might have already included windows.h without NOMINMAX, what we do is parenthesize all mentions of min/max, which inhibits preprocessor expansion of function-like macros. Look at our declarations of std::min()/etc.

> what we do is parenthesize all mentions of min/max

Oh! That explains some of the odd-looking code in <random>, since min and max are used as function names to determine the range of an RNG engine.

Bingo. We have a test that includes windows.h followed by all STL headers, to verify that we always remember the parens.