I'm aware of all of these things. But as your second citation points out, an officer legally entering a building during an exigent circumstance may confiscate and/or use as evidence anything found in 'plain view'.

> Requiring a warrant in all circumstances where the government wants to search and/or seize evidence is a cornerstone of a free society. Warrants are a trivial barrier if there is a legitimate investigation with any evidence at all. The "probable cause" requirement is a very low barrier.

We just went over a variety of obvious exceptions to the warrant requirement. You can argue that these are exceptional cases to be sure, but it is certainly not true that a warrant is always required nor should it be (as the comment I was responding to said).

A very slightly less clear-cut example is BAC, as the parent commenter mentioned. It is completely impractical to get a warrant in DUI cases. It would either be a completely meaningless waste of everyone's time, or it'd literally be a rubber stamp, where a cop calls up and receives the warrant with zero interaction or consideration from the judge. And I don't know about you, but i'd rather not open the door to true rubber-stamping of warrants. Because once you start doing that, it's only a matter of time until they start doing it with things that aren't so trivial.