I don't think that is quite right. Smith v. Maryland did not actually merely say it does not apply there. Smith v. Maryland said that installing a pen register to to record call detail information regarding an individual under surveillance did not need a warrant because:

1. The information was willingly shared with a third party.

2. The individual relied on the sharing for many other services including being able to trace harassing phone calls, and the like, and

3. The information was not deeply revealing.

The much more important case regarding 3rd Party Doctrine is California Bankers Association v. Shultz (1974), which established that there is no reasonable expectation to privacy in routine surveillance of bank records of transactions above a certain amount (set at $10k under the statute then as now). The thing is that the dissent was worried specifically about dragnet surveillance and the majority more or less swept that one under the rug.

However, this is not the 1970's any more and there are reasons to think the dragnet surveillance concerns that were ignored in 1974 carry more weight today. In 1983, the Supreme Court, in United States v. Knotts included clear dicta differentiating the case of following a car with a beeper installed in something that was sold with suspicion that it would be used illegally, from the dragnet surveillance case. Rhenquist, writing for the majority, said:

But the fact is that the "reality hardly suggests
abuse," Zurcher v. Stanford [460 U.S. 276, 284] Daily,
436 U.S. 547, 566 (1978); if such dragnet-type law
enforcement practices as respondent envisions should
eventually occur, there will be time enough then to
determine whether different constitutional principles
may be applicable.

The court further narrowed beeper tracking in Karo v. United States to hold it was a search when law enforcement officers determined that a barrel of ether (suspected of being used in making of narcotics) was traced to someone's home. Given that even without GPS, our cell phones are effectively beepers have lead some courts to start pushing back on subpoenas for historical cell site location data.

More recently, you have the 5 concurring justices in Antoine Jones v. United States, opining that long-term surveillance by virtue of time and amount of data collected may well violate the 4th Amendment even if individual pieces may not. I say "opining" rather than "ruling" because Sotomayor refused to rule on that ground, but instead chose Scalia's more narrow rule, while at the same time endorsing Alito's much broader rule. While not the "Opinion of the Court" it is still "an opinion of the majority of the court" and I think this has a certain amount of force on courts below.

We must be confronted that we are at a point where Rhenquist's insistence that dragnet surveillance must be considered separately now mandates that we confront that. A clear majority on the Supreme Court seems to believe that this can violate the Constitution with the other four justices merely having declined to comment on it.

I hope this clarifies both what the court said and what confusions there currently are as this area develops. No I am not a lawyer but I read Supreme Court cases for fun.