Nathalie, I agree with you lol, yes... in my country atleast, the metal fans ages range from 14 to 25 usually, you rarely see a man in his 30s listening and you will NEVER see a woman in 30s listening to metal.
The problem here in Bahrain is that people tend to relate Metal with immatureness, and so, people once they grow a certain age they start to think that they should grow up and break these "immature" habits and so they quit listening to metal.
Others become strictly religious and start forbidding metal as music in their lives
And some would keep on listening but they will stay away from the scene.
But I too think this might change in the future of our generation, with people being more open minded and all.