Its easier to tell in paper magic when you are getting close to drawing out your deck - but easy to ignore / not notice. I just played a game with an izzet deck that plays lots of cantrips and was surprised when I accidentally drew my last card - the same way you get a warning that you'll have to discard to hand size, it would be nice if there was at least a "are you sure" warning popping up when you are within one card of drawing your deck (especially if its on an opponent's turn and presumably you'd want to keep one card on top to protect your draw.)