I agree with Pat Mucci. There are several good strategic reasons to locate bunkers behind greens.
First, it affects a player's effectiveness at reaching a back hole location. A great example of this is at the first hole at Raynor's Mountain Lake. The first green is a double plateau. It's very important to have your approach end up on the correct portion of the green. The bunker at the back makes a player more likely to underclub in order to avoid it.
Here's a photo of the green from the right side. Note the hole is in the back.
No one in our group reached the correct level of the green with a few three-putts as the result. The back bunker is pretty intimidating. Photo is as viewed from the back of the green.
Another good reason for bunkers behind the green is to require distance control from those playing a ground game. One good example of this is at the eight hole on Doak's Ballyneal. This hole has a shallow, diagonal green. This photo is taken from the rear of the green. While it's easy to run a ball up, distance & line need to be good to avoid the rear bunker.
Rear bunkers can have a significant effect on line of play. On the second hole at Prairie Dunes, Maxwell uses the rear bunker to really make a player consider club selection. You don't want to be short, but if you reach the rear bunker then you have a very tough recovery to the multi-tiered green. It's easy to end up back in one of the front bunkers or at the bottom of the hill.
Rear bunkers can also affect strategy in a positive way. On the short par 4 16th at Holston Hills, out of bounds is very close to the rear of the green. Ross placed a bunker behind the green to catch balls that go long, provided you are approaching from the fairway. If you approach from an angle, no bunker to save you.
This is the hole from the tee. It's about 320 yards uphill.
This is the rear bunker from behind the green. Go over it and you're OB. This photo was taken during late fall.
I can come up with plenty more examples how rear bunkers affect strategy.