Some of the reasons many of the original "fore" (or topshot) bunkers were removed over the years by clubs (and other architects) were they were deemed to be either unnecessary genereally or unfair to weaker players (Wayne Stiles recommended that Gulph Mills remove all its topshot bunkers in 1940 for these reasons and they did it. Gil Hanse wanted to restore them in our current restoration plan but the membership didn't want the expense to restore UNNECESSARY bunkers).
Ron Prichard has speculated that Ross used them to function as something to catch topped shots so they would not run out on the hard (unirrigated) surfaces of the day to somewhere in the vicinity of a well struck shot. Apparently Ross hated topped shots! As an aside, Donald Ross, who was a very good player, used the low hooking shot almost exclusively in his own game which apparently was the shot of choice of Scottish players of his time. Also I believe that topped shots were more common in former times. Others believe that the topshot bunkers may have had a double function as sort of a foreground frame effect. Not sure I buy that one.
If you look carefully through the old aerials of many of Ross's original designs (Brad Klein's new book) you will see that Ross occasionally used bunkering in unusual and odd places (and sometimes in places that didn't really appear to come much into play). Some today might remark that is no more than bunker "eye candy". I'm not sure I agree with that either.
To digress slightly, I see that recently a new course, Pacific Dunes, was "critiqued" as overusing bunkering (placing bunkers in areas that weren't really in play). Some apparently believe that bunkering should be reserved only for places that have strategic merit and meaning. Others probably believe that bunkering, being one of the few holdover features of the original linksland courses (the beginnings of golf), think that bunkering should be random (as in nature) and should be used anywhere and everywhere simply to tie in and make bunkering seem consistent throughout a site. In other words bunkering in places that don't much function for golf makes the bunkering that does function for golf seem more indigenous to the general site and less like simply an odd relic used only for strategic purposes and function.
Personally, I think I would endorse the latter belief, although I recognize that it may be a cost and maintenance consideration in the minds of the clubs. Much has been done, though, to classic courses and their architecture (shrunken fairways, greens etc) simply because the stewards of those clubs fail to see or misunderstand the meaning of many of the elements of the course. Often some critics don't see that some things really weren't meant to apply to their own particular games and therefore recommend their removal. They fail to see that a designer like Ross may have been one of the best designers to include features (problems and solutions) for every level of player. He may have done other things simply as an artistic or architectural tie-in to other things that were functional! This may be one of the reasons that many of Ross's courses have been so heavily altered over the years.
There are a lot of things that go into these considerations, like our topshot bunkers, but I regret that ours were removed in the first place and I also regret that the present membership won't agree to restore them. If they restored them I doubt I would ever get in one (they were 100-125yds off the tees) but afterall they are what Ross built!