The third umpire said he had insufficient evidence to overturn the decision.
On field umpires make errors all the time; it's why the DRS was introduced in 2008.
However, Dar's incorrect decision on Saturday at the MCG is inexcusable.
Another Mitchell Starc bouncer during the morning session of day three hit the wristband of Mitch Santner's glove, and was caught by Travis Head at leg gully.
Marais Erasmus understandably called not out - the deflection was not obvious during live play - and Tim Paine called for a review after some deliberation with his teammates.
Sitting upstairs in the airconditioned third umpire's room, Dar had plenty of time to watch the replays and rectify the decision, footage from side on clearly showing the ball had struck the glove's wristband.
The elastic wristband visibly stretched up Santner's arm upon contact - no fancy technology was needed to decipher whether or not the batsman was out.
Dar spent a considerable amount of time analysing Snicko and HotSpot, which was not conclusive, and hastily rushed past the decisive footage.
Whether it was confusion, an over-reliance on technology, or just laziness, Dar's reluctance to overturn Erasmus' decision diminishes his credibility as a world-class umpire.
Fox Cricket commentator Mark Waugh voiced his disgust on Twitter, calling the decision "very poor".
"That is a very poor decision by the third umpire", Waugh posted.
"You can clearly see the band on the top of the glove moving after the ball brushed it. That type of decision is exactly why DRS is used in the game."
Cricket legend Shane Warne was similarly not pleased with Dar, suggesting the Pakistani should have taken his time and looked at more of the available footage.
"The sweatband clearly moved and it should have been overturned," Warne told foxsports.com.au.
"Sometimes the umpires get it wrong, but I don't think Dar sees enough of the vision either. He should have asked for more angles before making his decision and I believe he got it wrong."
Channel 7 commentator Ricky Ponting also heavily criticised Dar's decision.
"That has been missed by the third umpire, absolutely as plain as day … if you can't get that right, then you shouldn't be doing it," Ponting said.
"(The sweatband) clearly moves before it goes into the forearm guard. That in my opinion is conclusive evidence."
To rub salt in the wounds, Australia lost a review from Dar's mistake. Paine struggles enough with DRS as it is.
If Australia had not been in such a dominant position in Melbourne, Australian fans would be calling for the 129-Test veteran to retire.
Dar was awarded ICC Umpire of the Year in three consecutive years between 2009 and 2011, but hasn't received the accolade since the infamous Broad decision.
Joel Wilson was scrutinised for his umpiring during the recent Ashes series in England, and rightfully so - however, Dar's Boxing Day howler will go down as the worst umpiring decision of 2019.
