This could also just depend on how things are setup. For instance, in my httpd.conf file I include any modules by placing them in a directory, then calling them with...
Include /etc/apache2/modules.d/*.conf
Then, I have the file /etc/apache2/modules.d/70_mod_php5.conf...
# vim: ft=apache sw=4 ts=4
<IfDefine PHP5>
# Load the module first
<IfModule !sapi_apache2.c>
LoadModule php5_module modules/libphp5.so
</IfModule>
# Set it to handle the files
<IfModule mod_mime.c>
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
</IfModule>
AddDirectoryIndex index.php
</IfDefine
This is how its done in Gentoo. Why? I really have no idea, but it does make it pretty easy to see what modules are installed at a glance.
ls /etc/apache2/modules.d
Of course, its just as easy to run...
cat /etc/apache2/httpd.conf | grep Modules
So yeah.... I have no idea.