Breathing to both sides, usually every three strokes, is often taught as the correct way to swim freestyle. In practice, many fast swimmers breathe mostly to one side, especially in races.
Bilateral breathing can encourage a more symmetrical stroke and body rotation
Breathing every two strokes delivers more oxygen, which many swimmers prefer at higher intensities
In open water, being able to breathe to both sides helps with waves, sun and sighting other swimmers
A sensible approach is to train both, and choose by situation in races
If breathing to your weaker side feels awkward, start with drills: kick on the side with one arm extended, breathing to the weak side only, for 4-6×25 m. Then swim easy 50s breathing every three strokes. Keep the pace relaxed until the motion feels natural.