Tree pruning

Ok, Im being puzzled for some time now...Does anyone know of a new concept in pruning/lopping trees these days? I was taught to always prune tree branches at an agngle to allow water runoff. Over the past years I notice more and more that both domestic and public trees large and small are being lopped/pruned with straight across cuts. I do know the pruning rules for different plants, but the above pruning habit I notice sometimes work and sometimes dont. So is it a matter of the lack of knowledge of the person doing the job or a new concept that I have not read about?

[ 10. March 2008, 04:00 PM: Message edited by: Aster ]