Just making contact with a major league pitch is already incredibly hard to do

Making solid, hard contact is even harder

Many players do hit to both sides so they don’t get shifted by the defense, but many also focus on hitting it as hard as possible which means you give up some control over where the ball goes. The trend over the past couple decades has been to focus on hitting the ball as hard as you can rather than focusing on hitting it to a specific area of the field because the stats have shown that to be more effective.

If you’re hitting for power then you’ll naturally swing a little earlier on average because your bat speeds up through the swing, so if you hit the ball a little earlier you will hit it harder. But then it will also have the tendency to go in one direction. So a lot of power hitters tend to hit the ball to the same side of the field like 90% of the time. Batters who do this are often the best batters on their teams. Thus the defense shifts in order to limit the effectiveness of that batter.