When I grew up playing golf, one of the many things I had to learn about the Rules of Golf was that I wasn't allowed to move anything out of the way in a bunker. Even if there was a little pebble behind or in front of my ball. Maybe there was a small stick. Whatever it was, I couldn't move it, or I would face a penalty.
The idea was that, if a ball went into a hazard like a bunker, a player should not be allowed to create a cleaner look at the stroke.
However, under the new Rules of Golf in 2019, players are now able to move loose impediments in bunkers and penalty areas (formerly hazards).
Touching the ground in bunkers and penalty areas
One of the biggest changes in the new Rules of Golf was the decision to allow players to ground their club in a bunker or a penalty area. So, the new Rules of Golf treat penalty areas like the area "through the green," which is now called the general area. In the general area, players can not only ground their club, but they can also touch and move loose impediments. So, that's now allowed in bunkers and water hazards.
The idea wasn't necessarily to make playing from a hazard easier so much as making the enforcement of the rules relating to penalty areas clearer and leaving less room for interpretation. Many times, players were penalized for "testing the surface" of the ground in a penalty area when there was no intent and no advantage gained. Rather than continuing to enforce rules that led to harsh penalties, the USGA and R&A decided a player should be able to treat the areas similarly. After all, ground is ground. But on a golf course, there's certain ground -- or water -- where it's often impossible to play. Those are penalty areas, and that's the only thing that makes them unique compared to general areas.