Well...for starters...most aircraft are single engined with basic IFR instruments. Lots and lots of takeoffs and landings....weight measuring is more by collective and Q meter than scale. Cat A doesn't exist....load'em to the gills and gallop off into the mist. Lots of machines see a mechanic at the weekly crewchange...maybe. The FAA takes a blind eye to what goes on down there....competition is cut throat.....scud running is the norm even for most IFR ops due to communication problems getting clearances, weather and such. The oil companies safety programs are a joke...the operators safety program is even worse. Throw in a large dose of complacency....and you have a recipe for disaster.
A serious study of the accidents and causes would be an interesting thing.....remember the R-44 that went down at night...the series of fuel contamination accidents Air Log had....the rash of crashes PHI had....every operator has had problems at one time or another....it is like they take turns somehow.
Compare that to the North Sea....and you have your answer. There's lots of good hard working folks there...but the infrastructure lets them down.