These standards make sense. The bottom line of the Fourth Amendment to our Constitution is that the police cannot stick their noses into your life and search your person, your home, or your belongings without some reason to think that you are up to no good. George Washington, Thomas Jefferson, James Madison, and other founders of our country had suffered searches and intrusions by King George's colonial agents, and they therefor put these restriction into the Bill of Rights. Consent searches turn this entire way of doing things upside down. When they have no evidence but just a hunch or just feel that a search might pay off for reasons they perhaps can't even articulate, officers can simply ask for permission to search.
Citizens have a right to refuse.
In practice, few do. Most do not know they have a right to say no. Many think that if they do refuse, the officer will consider them suspicious or think they are hiding something, and do the search anyway. Few citizens wish to displease authority, and the police officer, with uniform, badge, and gun, is the living, breathing embodiment of state power. All it takes is a little verbal finesse.