Patrick,
The original man made bunkers were sometimes grassed vegatatively, with grass plugs, spaced a foot or so apart, and seed scattered in between the plugs. This method was used in areas where we might use sod today. I think it was developed first in the heathlands, and then brought here. Some of these people placed plugs inside of a bunker and it grew. And then they decided that they liked the effect of that. Maybe they thought that it made the hazard more intimidating? Maybe they thought that it made the hazard look more natural?
So I don't think you will ever see the end of it like you do with fads. I think just as then, you will see people making the same experiments. So it will reappear somewhere else until someone decides they don't like it and it's removed. And then 100 years later it will make another appearance, who knows, in the same bunker.