The 4th amendment most directly affects the conduct of the police, which makes it the most important to policing. I don't think it has been all that broadly interpreted but it has been interpreted to allow suppression of evidence seized because of a violation of the 4th amendment. Not requiring suppression of such evidence would put the courts
in the position of condoning lawless behavior by the police.
The remedy of suppression of evidence for 4th amendment violations has made the police act more responsibly over time. Of course the policeman's job would be easier if he could search anywhere any time without a warrant or some valid reason to search. But the people have rights of privacy from such intrusions, and the amendment says that clearly:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause
, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
The reason for the warrant requirement was to protect people from the overbroad general warrants the King used before 1776.
Does this answer your question?