/etc/environment, variables aren't expanded

[TomasN]

Hi. Why the environment variables in /etc/environment aren't expaned?

JAVA_HOME="/opt/jdk1.6.0_06"
JDK_HOME="$JAVA_HOME"
JRE_HOME="$JDK_HOME/jre"
PATH="$JDK_HOME/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"

... in /etc/profile each variable in quotes is expanded.