It's not and its not really one of the reasons. A lot of us are on reddit as well and facebook used to be very popular. Our privacy concerns are a bit weird. On one hand we distrustef google street view so much that google gave up on the other we use our full names on facebook and have our last name on our door bells. I think the real reason so many of us are on reddit and the fediverse is just that we are 84 million people and enjoy it to talk in german where we can. More populous countries often either have less available internet or speak english natively or are more comfortable speaking english than us.