The proper place for rakes is either all in the bunker, or all out. Half in and half out drives mowers and bunker rakers crazy.
Adrian nails it, others have added some good points. BTW, yes, clean edged water is generally considered to speed up play. But, must not have safety shelves. Balls under water appear bigger and thus closer than they are, making golfers think they can retrieve them, but often causing them to fall in the water themselves.....
The bigger, and so far ignored, part of the question is whether they are worth it?
Of course, there is no blanket answer, but I believe the 80% bell curve probably applies.
For the bottom 10% of courses, which should be intro to golf, golf factories, etc., none of them are worth it.
For the top10% of courses, some to many are worth it to create a unique and challenging course.
For the 60% of courses in between, they should be used sparingly, probably limited to where they are forced to occur naturally, with the designer consciously avoiding play slowing features of any other type.
Yes, it can reduce the quality of design, but only if you subscribe to the "there is only one way to skin a cat" theory of golf hole design. Is a forced carry, sand bunker front right of green, or deep rough really the only way we can make that hole perfect? And, for courses that seem to be an ever increasing difficult business proposition, is perfect design the real goal? In theory, a good architect could design a great course with zero sand bunkers, using creativity.
In fact, one could theorize that the reduced popularity of golf is in part attributable to all us designers ignoring the real needs of the typical golf course in favor of self glorification (us or the owner) of a tough course, when its not needed.
Moving forward, if every golf survey says the decrease in players is linked to time to play, slow play, etc., it would follow one of the top design criteria would be to specifically design for speed of play, as form follows function.