platform specific qmake versions ?

Hello,
the installed NokiaQtSDK installed on Ubuntu includes several platform specific qmake executables - why different versions are necessary, can not only one qmake executable (which fits to the development platform) be used to generate makefiles for the specific target platform?

root@sa-desktop:/opt/NokiaQtSDK# find . -name "qmake" -exec ls -l {} \;
-rwxr-xr-x 1 root root 908 2011-01-12 17:48 ./Maemo/4.6.2/madbin/qmake
-rwxr-xr-x 4 root root 4183692 2011-01-12 17:51 ./Maemo/4.6.2/tools/qt-tools-4.7.0-m0.20.32-linux/bin/qmake
-rwxr-xr-x 4 root root 4183692 2011-01-12 17:51 ./Maemo/4.6.2/targets/fremantle-pr13/bin/qmake
-rwxr-xr-x 1 root root 13890437 2011-01-12 17:47 ./Simulator/Qt/gcc/bin/qmake

thanks + best regards
Andjesto

One would be enough but then you'd have to pass appropriate options to qmake to invoke it for different platforms which is a too difficult task for many inexperienced developers.