Why do helicopters have skids?
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Larger helicopters have landing wheels, and as we can see on the picture above, they are placed as far outward as practically possible in order to provide stability in the landing. Touch down one wheel on an sideways inclined slope, lower the collective, and the helicopter will align itself onto the slope with:


The location of the Centre of Gravity (CoG) always in between the wheels. The higher the CoG, the wider the landing gear impact points must be.
The weight being supported on clearly defined and structurally reinforced points. Even if the bottom of the helicopter is perfectly flat, the landing ground may not be, and to support all of the weight at any random point at the bottom requires a lot of relatively useless weight for the re-inforcement.
The behaviour after first wheel touchdown being clearly defined. The wheel is a point of impact upon the landing plane, mathematically much more defined than a plane of impact upon a landing plane if the latter is curved.


All the above is for wheels, which allow the helicopter to taxi on-ground. Skids perform all of the above functions apart from the on-ground taxiing, and are cheaper and lighter than retractable landing wheels. Of course, the other downside is that they have more drag.



One would not want to land this helicopter without the skids!