The purpose of being visible goes hand in hand, but beyond the action. So, think about different positions that require a uniform (police, nurse, pilot, etc.). These people have the expertise but if a pilot in plain clothes walked up to your flight to fly the plane you’d probably take issue because you don’t know they’re actually a pilot. And even if a doctor could tell you verbally everything they know about medicine and healing, if you went in the hospital to receive aid and the doctor had on a sweatsuit and baseball cap, you probably wouldn’t trust them operating on you or someone you know. Islam is very important to show outwardly for the same reasons. People with good hearts and do good things can all be grouped into being something else, but as Muslims giving “dawah” is a part of our faith. Dawah is a way of inviting people to learn of the faith without coercion and that requires people to know you are who you are because of your Islam. It is an integral part of who we are. So, if you see me and you have no idea I’m a Muslim and potentially group my actions with another entity, it diminishes that mission.