100% agree that bunkers have become overbearing and too often their existence is driven more based on aesthetics and framing vs. strategic benefit. Especially on relatively flat land, where a sea green provides very little contrast to the players eye. The bunker is seen as a tool to help frame the hole.
I would also agree that the high standard of bunker maintenance has an influence on the frequency of bunkers across a course. If playing out of a well manicured bunker is of a similar challenge to playing out of rough, the impact of the bunkers placement on a players round is not significant.
Which in lies the problem, If the modern bunker provides little strategic value to play and is mostly visual, does the visual benefits outweigh the additional maintenance cost? On the whole I'd say no. But I also believe that bunkers should provide a greater penalty to a player than surrounding rough. If a bunker is suppose to be a hazard, it should be maintained closer to that of a hazard.
If high level maintenance standards were lessened, and bunker conditions were left more up to chance, The penalty of playing a ball into a bunker would dramatically increase, causing the overall difficulty of courses with a very high number of bunkers to skyrocket. Courses electing to restore some more hazard to their bunkers would be best off dramatically reducing their bunker count. Choosing to keep only the most strategically valuable bunkers and converting the rest into grass bunkers.
It's probably not viable to allow the bunkers to be left up to nature for maintenance, but rather I'd like to see bunkers raked by the maintenance staff no more than twice a week( i.e. Mondays and Thursdays) and with a wide toothed rake. The goal would be to smooth out most of the large imprints and redistribute sand that across the bunker. Players can be asked to smooth over their own tracks after a shot, but between maintenance raking the bunkers would be left up to chance.
I recall a comment Ian Andrews made years ago about working with committees around tree removal, asking the members of the committee to each flag the 25 most critical trees on the property. I could see the same exercise being done with bunkers. If a bunker has no strategic value, remove it. By reducing the number of bunkers and increasing the challenge of a bunker recovery, each bunker's existence takes on a greater role, while allowing the course to be maintained at a lower cost.