I see I'm back to this thread like a moth to a flame, my third go over several years . . . but at least I'm somewhat logically consistent.
We are working on two projects currently that will be bunker-minimal if not bunkerless.
The current one is Memorial Park in Houston. When Brooks Koepka signed on as the consultant, one of my first questions to him was whether he would mind if we built a course with few or no bunkers, and he didn't have a problem with the idea, saying bunkers are rarely a factor in his strategizing. The TOUR is on board with the idea, because it minimizes clean-up issues during rain delays. Also: bunkers slow down play for municipal golfers, and add to maintenance costs.
So, we've been using the ravines that are on-site, new ravines that we've added, the large irrigation pond, and the trees to challenge players, and keeping bunkers to a minimum. There will be nine bunkers on the back nine, and none at all on holes 13, 15, 16 or 17. There may be a few more on the front nine, but we'll be comfortably under 25 for the whole course.
The other project where I have considered zero bunkers is in northern California. That property is blessed with oaks, vineyards, rock outcroppings, and a stream that comes into play on seven holes, plus the most dramatic elevation changes of anywhere I've worked. I would be happy to build it without any bunkers, except that there are restrictions on what I can and can't do in the buffer areas around the streams, and I believe that an occasional bunker in those areas would be better than a lot of grass with restrictions on when it can be mowed, especially right next to the greens. So my bunkerless course may have to wait a bit longer, but I'm trending in the right direction.
P.S. Technically, Tara Iti is bunkerless, but there sure is a lot of sand in play.