Because anyone who knows his/her business about carrying concealed, knows how not to be noticed.
You miss the point, if YOU should have to defend yourself, and have been in LV for more than 24 hours, YOU are subject to prosecution for failing to register your means of defense.
It has nothing to do with how effectively you conceal your defense weapon.
It does have to do with how you will be treated by L.E. when they decide YOU are some sort of bad guy for failing to comply with their B.S. law.
Do you really want to risk L.E. taking a negative attitude against you in a case that can have it's direction decided by the first cop to respond, or some ambitious DA?