Well, popularity-wise it has about 0.003% of the web server market. So I wouldn't put too much stock in that. We also have yet to ever see a user request for it.
As to user request, here is one :-)
http://bugs.php.net/bug.php?id=42987
One of the reasons why did not receive much requests is that we tried our best to make it easier for our end users, including a pre-built PHP binary, tutorials, web GUI for building the PHP binary, etc. But it still requires extra devel-packages like autoconf, m4, etc.
Best Regards,
George