I would have thought there was less copper work on roofs now than there was 50 years ago. 1000's of buildings built in the Victorian/Edwardian era from small chapels to huge mills had roof ventilators like this,
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there were also decorative finials on the ends in many cases and many a building was adorned by a copper weather vane. While not as easy to work as lead quite a lot ended up as flashing on roof work because it was easy to handle rather than any anti microbial properties. Like lead the stuff has almost become too valuable to use in some circumstances and with demolition of the type of buildings likel schools,chapels factories that had copper features and sometimes substantial copper lightening conductors I wouldn't be surprised if there was less copper about now on roofs than for many decades. Additionally here were 1000's of miles of bare copper telephone wires for a good part of the 20th century getting covered in grime from smoke. Some must have run above and dripped contaminated rain drips on damp mossy ground especially in woods and Railway cuttings. Perhaps a study would show if a super moss has evolved in such places.
G.Harman