Having access to powerful cards for low prices means new players can easily pick up the game
The legendary cat knight at launch was valued at around $25 to $32, despite its Commander 2017 version having a value of only around $6
It doesn't copy whether that creature was tapped or untapped, whether it had any counters on it or Auras or Equipment attached to it, or any non-copy effects that had changed its power, toughness, types, color, or so on
If you cast Liliana and use the +1 then at that point you are pretty much worse of than you would be casting dribble like Mind Rot in terms of immediate impact on the game
This makes them great choices for questing, as its much harder to remove them from play
A regenerated creature keeps all its enchantments on it, so Molting Snakeskin remains useful as long as you can pay for the ability