In the West you only need 1 person, who doesn't have to be credible, in the Quran, you need four witnesses, all of whom have to be of good standing. It's a lot easier to get away with rape in the west (particularly in places like the UK), than it is in the Muslim world - of course that gets cancelled out by the lack of reporting of rape in the Muslim world because of the fear of shame and of potential reprisals.