A horse is a rather expensive lawn ornament if it is not used for anything. I believe that humans and animals need a sense of purpose to their lives. Both become bored with inactivity. For most of human history horses were employed in working roles and this was not an issue. However, in modern times horses have been supplanted by mechanization and the question of what you plan to do with a horse is a real one. There are a lot of possibilities and in the end it is what you find enjoyable and the aptitudes of your mount.
The total population of horses is down from its peak in the early 20th Century but in my own state of Maryland the 2010 Maryland Equine Census showed a total of 79,100 equines of various types, including donkeys and mules. For a relatively small state and an animal whose working utility has been mostly been supplanted those are still significant numbers. It is clear that many people still have horses in their lives.
In my series on equestrian sports and activities I will look at the various things riders do with horses. I am a trail rider. I find it a relaxing break from and stresses and strains of modern living. However, I have engaged in other equine activities as a participant or spectator and have friends who have done even more.