Mushrooms in the forest, cars in the city, snow in the mountains, cows in a field, the sky is the limit and the earth is the other limit. Da Vinci said that to master art you need to master all mediums and subjects. At the end of the day, the challenges of landscapes make you a better artist and get you one step closer to mastery.
I spent all of my time as an artist developing my craft painting and drawing animals and humans because I thought it was more challenging and that anyone could paint landscapes. Boy was I wrong and know not only do I enjoy landscapes immensely it has drastically improved my overall artistic ability.