There's an argument to be made that not making the call when the result was already certain, even if the margin of 0.5% hadn't been reached yet, was irresponsible in the sense that it allowed Trump more time to promote this idea that he has won, everything's fraudulent etc. (Just look at his last tweet: https://twitter.com/realDonaldTrump/status/13250998450450718...)
I disagree with that argument FWIW, but I can certainly understand it. Though I think people were just impatient to hear "Biden has won" be made official, even if they already knew. I certainly was.
the result was definitely not certain. there was more outstanding votes than the leader's margin, and it wasn't clear what the composition of those votes was. it was definitely very likely that they would follow the trend of the rest of the state, but it could have come to pass that the late-arriving absentee ballots or provisionals in PA broke very differently to the early-arriving absentee ballots. They called it when the first sample of outstanding allegheny county ballots were counted and made it clear that the rest of those votes were going to trend as expected.
the networks have to balance a late call giving fodder to conspiracy theorists with an early or uncertain call also giving fodder to conspiracy theorists. they don't want to be doing anything that could promote a narrative claiming the networks are trying to influence the election for biden.
I disagree with that argument FWIW, but I can certainly understand it. Though I think people were just impatient to hear "Biden has won" be made official, even if they already knew. I certainly was.