The purpose of such rules in practice is to help the American public to sleep at night despite having tacitly authorised a nightmare. You know the scene in Casablance, even if you've never watched the movie - it has permeated our culture Captain Renault claims to be shocked to discover that the club is being used for gambling, undercut by a croupier giving him his winnings.
If you don't want spooks to do what spooks do, don't pass a law saying it mustn't happen, don't vote for a government that promises they'll exercise oversight over the spooks to prevent it. Just get rid of the spooks. Congress could, if the American people wanted - which they do not - abolish these agencies entirely. They'd just cease to exist and while I'm sure some small scale abuses would continue you just can't run programmes to snoop these huge volumes on pocket change, and companies would be less likely to co-operate with informal requests than with the Department of Justice.
But as much as they enjoy bluster, Americans are afraid, and so the spooks will certainly continue to be authorised and "outrages" will happen when once in a while it is revealed that the spooks are doing what spooks do but nothing actually changes. Eventually it'll get to be so routine the The Onion has a pre-built news article for it like for the mass shootings.