I would tend to prefer they be marked as such too, but Decision 33-8/41 clarifies all of this:
If an appropriate authority prohibits entry into and/or play from an area for environmental reasons, it is the Committee's responsibility to decide whether an environmentally-sensitive area should be defined as ground under repair, a water hazard or out of bounds.
However, the Committee may not define the area as a water hazard or a lateral water hazard unless it is, by Definition, a water hazard. The Committee should attempt to preserve the character of the hole.
Those could have been marked as water hazards. Sometimes courses will mark water hazards that are also ESAs by putting a green cap on top of the stakes. They clearly mean "do not enter this area" (as all ESAs do) and they still play as water hazards and afford players those same options.
If they marked water hazards as OB, then perhaps they shouldn't have.
More from the same Decision, including some examples. Bolded text is my doing.
(a) A small area of rare plants close to a putting green has been declared an environmentally-sensitive area. The Committee may define the area to be ground under repair or out of bounds, but it may not be defined as a water hazard or lateral water hazard. In view of the area's proximity to a putting green, it should not be defined as out of bounds because a stroke-and-distance penalty would be unduly harsh. It would be more appropriate to define the area as ground under repair.
(b) A large area of sand dunes along the side of a hole has been declared an environmentally-sensitive area. In contrast to (a) above, it should not be defined as ground under repair because the absence of a penalty would be unduly generous. It would be more appropriate to define the area as out of bounds.
(c) A large area of wetlands along the side of a hole has been declared an environmentally-sensitive area. As in (b) above, it could be defined as out of bounds, but it would be more appropriate to define it as a lateral water hazard.
An environmentally-sensitive area should be physically protected to deter players from entering the area (e.g., by a fence, warning signs and the like) and it should be marked in accordance with the recommendations in the Rules of Golf (i.e., by yellow, red or white stakes, depending on the status of the area). It is recommended that stakes with green tops be used to designate an environmentally-sensitive area.
While I understand the logic of these decisions, the fact that you can`t have a hazard without water makes it an all (stroke and distance) or nothing (free drop) situation when there isn`t water involved. At the very least, I think a course designer should have the option to create a non-water hazard that is played similar to a lateral WH. In example A, they say it should not be defined as OB because of the proximity to the green with the stroke and distance penalty being too harsh.
Today, I was playing with a guy in his 20s (age, true handicap would be higher) who has been playing for a year. On the 5th hole at the Keystone Ranch course, the white tee was 183 yards to the middle of an elevated green with a slight wind behind us. It is 140 yards to carry the ESA lateral water hazard (where they provide a drop area about 30 yards short of the greeen). 10 yards over the green is some lush grass almost 2 feet tall where losing a ball is likely. The guy makes his best swing of the day and nuts a 6 iron that flies the green into the long grass. Result- lost ball. Needless to say, he was quite dejected. He would have better off chunking one 40 yards into the ESA hazard and being able to take the penalty drop near the green.
I agree with the USGA that stroke and distance can be too harsh in some situations and a free drop too lenient. IMO, cutting the grass down 10+ yards over the green would detract from the look and character of this hole while adding hazard stakes would seem appropriate. With this being the case, why not give the course architect and/or greens committee the option of creating a non-water hazard to best represent the character of the hole while providing a fair penalty for an errant shot?