President Joe Biden delivered his State of the Union address Tuesday night, and despite the electric atmosphere known to prevail in the House chamber during such events, four of the nine justices on the U.S. Supreme Court decided not to attend, as The Hill reports.

Though the justices' attendance at the speech is by no means compulsory, the presence or absence of particular members of the high court on a given year tends to spark speculation as to possible underlying rationales.

Five justices attend address

According to The Hill, the jurists who opted for an in-person State of the Union experience included Chief Justice John Roberts and Justices Elena Kagan, Brett Kavanaugh, Amy Coney Barrett, and Ketanji Brown Jackson.

In addition, two former justices, Stephen Breyer and Anthony Kennedy – known for their regular State of the Union attendance during their tenures on the bench – also turned up to hear the address.

No retired justice had accepted an invitation to a State of the Union address since 1997, when Byron White was in the chamber for then-President Bill Clinton's remarks to the nation.

Justices choosing to sit Biden's speech out were Justices Samuel Alito, Clarence Thomas, Neil Gorsuch and Sonia Sotomayor.

Alito's absence

As The Hill points out, Justice Alito has not attended the annual event since 2010, when he was embroiled in controversy for appearing to say the words “not true” under his breath when then-President Barack Obama took aim at the high court for its ruling in the campaign finance case of Citizens United v. FEC.

NBC News noted at the time that during Obama's speech, the then-commander in chief ripped the court's decision, saying, “[w]ith all due deference to the separation of powers,” the high court “reversed a century of law that I believe will open the floodgates for special interests – including foreign corporations – to spend without limit in our elections.”

Obama's critique prompted Alito to, as NBC News put it, make “a dismissive face, [shake] his head repeatedly and [appear] to mouth the words 'not true.'”

Then-Vice President Joe Biden took issue with Alito's reaction, agreeing with Obama that the Citizens United ruling was "dead wrong” and asserting, “[t]he president didn't question the integrity of the court. He questioned the judgment of it,” and Sen. Patrick Leahy (D-VT) opined, “There were days when judges stayed out of politics. It would be nice to go back to those days.”

“Like potted plants”

In 2015, Alito provided some additional context for his personal reluctance to attend State of the Union addresses, speaking at length to the American Spectator, as Business Insider noted at the time.

Offering his unique perspective on the SOTU scene, Alito began, “It's very strange to go as a justice. We sit there like potted plants.”

The justice continued, “We sit there, and the president will say something, and members of the president's party will stand up and start applauding. Members of the other party often will not. But every once in a while, the president will say something that is nonpartisan.... [t]hen everyone's applauding and standing.”

“We look foolish sitting there,” Alito went on, “so we stand up and start to applaud. And then we'll get faked out. The president will say, 'This is a great country' – and everyone will stand up and start to applaud – 'because we're gonna do this, we're gonna enact this legislation.' It's a very odd experience.”

Thomas takes his leave

Also giving Biden's speech a miss was Thomas, who, as The Hill notes, has not attended a State of the Union address since 2006.

The highly charged political nature of the event also appears to have put Thomas off the idea of appearing in person.

According to the New York Times, he told a law school audience back in 2010 that he prefers to remain absent due to the fact that it is “very uncomfortable for a judge to sit there,” because the proceedings are “so partisan.”

Providing a somewhat unflattering insider's view of what truly goes on in the House chamber on the night of the speech, Thomas added, “There's a lot that you don't hear on TV. The catcalls, the whooping and hollering and under-the-breath comments,” though it remained unclear as to whether that atmosphere played any role in the decisions from Gorsuch or Sotomayor not to attend.