Why are there locale troubles under Windows?

I will report a snippet from http://php.net/setlocale

Warning The locale information is maintained per process, not per thread. If you are running PHP on a multithreaded server api like IIS or Apache on Windows you may experience sudden changes of locale settings while a script is running although the script itself never called setlocale() itself. This happens due to other scripts running in different threads of the same process at the same time changing the processwide locale using setlocale().

I spent about 2 seconds before thinking: can it really be? I mean, is there no way to set locale info per thread? And after a brief web search I came up with this keyword: _configthreadlocale Read more at http://msdn2.microsoft.com/en-us/library//26c0tb7x(VS.80).aspx (beware, this page is very slow or their servers are anyway). Looks like this function exists since Windows 95 and guess what it does: it affects the behaviour of the locale functions so that _each thread will have indipendent locale settings_. So, I though: WHY? Why does not PHP use such function in the windows binding? Let's be clear, I don't think to have found a solution that (the great) PHP developers could not find, but I would like to know why they did not fix the bad behaviour of PHP's setlocale() function using the _configthreadlocale() win32 function, there must be some reason I really could not think about up to now. I really hope somebody can point me to something to read about this topic (I found pretty nothing up to now) or better directly explain it to me. Thank you -- Daniele C. -- We make a steel CMS, Drake CMS