Oddly no one else seems to be reporting this.
Penn reached the point of no return for Rump. He has no chance of winning. There aren't enough votes left to make up the deficit of over 35,000 votes to tie the election. It's over. Plus, there aren't enough votes left to even make take it to the 20,000 mark to force an automatic recount. The others are playing it real safe, that's all.
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Vox live results: Biden wins Pennsylvania
The real reason that the mainline news is reluctant to call it is that Rump declared himself the winner early on when he had a lead. Later on today, they will be following suite. The count is now beyond Rump even getting a forced automatic recount even if he gets most of the remaining outstanding votes which is beyond comprehension.