One thing I harp on a lot is leading and handling from both sides regularly. Aside from helping your horse be comfortable with a wide variety of sights, experiences, and positions, leading from both sides is good for your horses posture.
Most horse folks learned to do everything from the left. We don’t even notice how often we do stuff on the left side. We halter, lead, saddle and mount from the left side. When’s the last time you did stuff from the right? If it felt awkward, it might not have lasted that long before you went back to the comfortable side.
But unfortunately, this has postural ramifications. From the first halter we put on a foal, to interactions done day in and day out, we are building postural habits in the horse. The ones shown in these photos are ones I see very often, and they are the result of (among lots of other factors) habitual handling on the left side.