We were adding a lot of new cards to collect with the Booster Fun initiative (see here if you don't know what I'm talking about) and wanted to make a booster that helped the collector have an easier time collecting all those hard-to-get cards
so far I have a complete set of all Planechase cards, almost a complete set of all Archenemy cards, the 3 Challenge decks from original Theros block including all heroes and hero items, a set of the Explorers of Ixalan tiles, and I am in the process of constructing a Momir Basic offline cube
Vivien, Champion of the Wilds A nice card for green stompy decks in EDH, the static flash ability helps protect Vivien, Champion of the Wilds from attacks
Giving your opponent access to that isn't always ideal, but you get it first, so I think it ends up benefitting you more often than it benefits them
you can tell them if you'd like, but they may take that as a sign to get up and go for a walk