When I was in high school ('86?) coming home from my part time job I was stopped once and they asked to search the entire car so I said ok. I had nothing to hide and I was a teenager vs. two cop cars and several officers.
. They searched the trunk, under the seats, everything. In the end they said my car just fit the description of some criminals they were looking for and sent me on my way without the speeding ticket I deserved.I don't think most LEO's are Buford T. Justice types trying to throw their weight around. I think they are just gathering information and what they get from you, even if not incriminating, might help them connect the dots about something important.
Of course we could all avoid being questioned by just not breaking the law in the first place.