Most passengers weigh the skills of a pilot based on the hardness of his/ her landing. This is a flawed judgement, because a smooth landing is not necessarily a safe landing. Any well trained pilot could make his landing extremely soft by floating the aircraft and holding it off the runway longer. But this is not what is expected of a pilot. When we are trained on airliners the first thing instructors always want to see is a well stabilised approach. A stabilised approach is very critical in a high performance aircraft (most of the airliners).
So, what do I mean by a stabilised approach? Without getting into any technical details, when a pilot is doing a stabilised approach the amount of controls or thrust lever movements he has to make to keep the aircraft on the correct trajectory for landing is small. He maintains the correct approach speed. He is on the centre line of the runway and most importantly, he closely maintains the crucial three degree glide towards the runway. When done so, the aircraft will pass over the end of the runway (threshold) at 50 ft. And from there, a good landing is one where the pilot touches down preferably, within the first 1000 ft of the runway with an adequate vertical speed. A firm landing, which some passengers think is hard, is not necessarily bad as long as the pilot gets most of the things mentioned above correct.
From all those points mentioned above, the most critical thing is getting the airplane down on the correct place. Floating over the runway in the hope for a smoother touch down is downright bad airmanship. As the famous aviation quote goes: There’s nothing more useless than runway behind you and altitude above you! This is a very true statement. Landing long on the runway increases the chances of an overrun specially when landing into short fields. It also increases wear on the engines and brakes.
So, the answer to your question. Pilots do not find it difficult to land the aircraft smoothly. They are well trained to know what is safe and what is not. I am not saying all hard landings are done on purpose. Sometimes, pilots get it wrong and land very hard. The landing gear is usually able to take the load. In an A320 for example, it is not considered a hard landing unless the vertical g-load on the touch down exceeds 2.8 gs, which is quite a lot. A typical firm touch down rarely exceeds 1.5 gs.