In part this is a quality of life thing -- it's nice to see if you would have drawn an out if you had had just one more turn.

But it also has gameplay implications. In game one of a recent Bo3 match I lost in fairly short order to a mono-red deck after getting color screwed. The turn they finished me off they started with a Mishra's Bauble, looked at the top card of my deck, then finished with several burn spells.

Did opponent see my other color? Did they see a key card from the deck I was playing? In paper, I'd be able to tell. On MTGO, I'd be able to tell. But on Arena, I can't.