Avoiding conflict is always #1 priority. However, you can't control the minds of others who wish to do harm.
Running out of ammo in your primary magazine is only one factor to consider. What will you do if you have a malfunction? Also, you don't need to run out of ammo in your primary mag to warrant a mag change. A full mag is always better than a half-full mag.
There are MANY benefits of carrying an extra mag (of whatever size), with little to no drawbacks.