If you are holding your phone normally the iPhone doesn't have speakers that it can use for the left and right channels. Try turning your phone on its side to get a better stereo effect.

The grills at the bottom of many iPhones cover a single speaker on the right side, and the microphone and other sensors on the left side.

Try turning your phone on its side and you should find that one channel (left or right) comes out of the speaker at the bottom of the phone. The other channel comes out of the speaker you hold against your ear during calls.

For one thing if your headphones are wired backwards (the left sound comes out of the right earpiece) that is a good indication that they are fakes.

If you are listening to music then only musicians care if it sounds like the drummer is playing a left-handed kit. But, films will use sound to help place the actor or action on the screen, or indicate events off-screen.

For some games it's essential. You want to know which side the enemy is coming from.