Inheriting Maven profiles

I'm in the process of moving a number of projects from Ant/Ivy to Maven. Many of our projects use Thrift and we use a Maven Thrift plugin to conveniently compile our Thrift IDL. Given that all of our Thrift projects have the same setup, the plugin is declared in a our parent POM.
The plugin is declared in a profile that is only activated when a thrift source directory is present:

  <profile>
    <id>uses-thrift</id>
    <activation>
      <file>
        <exists>${basedir}/src/main/thrift</exists>
      </file>
    </activation>
    <build>
      <plugins>
        <plugin>
          <groupId>org.apache.thrift.tools</groupId>
          <artifactId>maven-thrift-plugin</artifactId>
          ...

I actually have a number of plugins defined in such profiles so that they become active only when relevant source artefacts are present in the sub-project.

This all looks good, but in practice I found that the profiles were never activated in sub-modules that were being built from a parent project. It was as if the activation state was determined at the parent level, not on a per module basis.

It seems that profile inheritance does function as I expected in Maven 2. It does however work perfectly with Maven 3.