Well, if an officer wants a warrant to check your house or car there has to be a GOOD reason! He can't just say something like "Hmmm… Their house is red, that seems sketchy! I'll get a warrant!" that is NOT probable cause! But, say someone is a wanted criminal, this is a GOOD reason to check their house, just in case there is evidence that can help them in the case against the criminal.
I hope this helps!