I'm actually a qualified live sound engineer. How is that relevant? Well, we had to study how the ear perceives sound. And it's not just a funnel for the sound to enter into the opening to reach the ear drum.
The ear itself in its shape but also how it's made is important for periphery hearing. Yes, like we have periphery vision, we also have periphery hearing. The ear is slightly porous and when we detect the direction of a sound like to our side or behind us it's because of the air molecules carrying the sound waves hitting and penetrating the outer-ear which is interpreted by the brain to recognise the direction the sound is coming from.
When the ear changes shape and cauliflowers due to calcification the effectiveness of our periphery hearing becomes greatly reduced.
This is an issue because we probably take out periphery hearing for granted. Something as simple as crossing the road where we hear a car come out of nowhere for example, so we can react accordingly.
Your hearing is important, ergo your ears are important. Your eyelids protect your eyes, but there's nothing to protect the outer ear because in normal day to day life there's little risk of damaging them and they're relatively durable otherwise. But the abrasive nature of grappling didn't factor into the evolution of the ear, so wear ear guards if you're concerned about your periphery hearing.