When I create complex type hierarchies (several levels, several types per level), I like to use the final keyword on methods implementing some interface declaration. An example:

interface Garble {
  int zork();
}

interface Gnarf extends Garble {
  /**
   * This is the same as calling {@link #zblah(0)}
   */
  int zblah();
  int zblah(int defaultZblah);
}

And then

abstract class AbstractGarble implements Garble {
  @Override
  public final int zork() { ... }
}

abstract class AbstractGnarf extends AbstractGarble implements Gnarf {
  // Here I absolutely want to fix the default behaviour of zblah
  // No Gnarf shouldn't be allowed to set 1 as the default, for instance
  @Override
  public final int zblah() { 
    return zblah(0);
  }

  // This method is not implemented here, but in a subclass
  @Override
  public abstract int zblah(int defaultZblah);
}

I do this for several reasons:

1. It helps me develop the type hierarchy. When I add a class to the hierarchy, it is very clear, what methods I have to implement, and what methods I may not override (in case I forgot the details about the hierarchy)
2. I think overriding concrete stuff is bad according to design principles and patterns, such as the template method pattern. I don't want other developers or my users do it.

So the final keyword works perfectly for me. My question is:

Why is it used so rarely in the wild? Can you show me some examples / reasons where final (in a similar case to mine) would be very bad?