It’s my understanding there are a number of shooting grounds and/or driven shoots in the UK that require fiber wads because of objections to plastic wads. Steel shot and fiber wads would not work because the thick plastic wad protects the bore from the inevitable scoring that steel shot inflicts on shotgun bores. Another seeming obstacle. There are trap clubs here in the US that have been forced to use steel shot for ATA trap. They reload and seem to get along fine, but plastic wads are necessary.