Core Sets have been home to any number of hype-inspiring and format-defining cards since the change in design philosophy, from Baneslayer Angel and the Titans to the Rootbound Crag cycle of dual lands
That helps to actually reach the top end of your mana curve, rather than simply losing the game because you kept drawing the expensive cards that you couldnt castwhat we usually call mana screw. Its also worth mentioning that landcycling abilities do count as cycling for the purposes of cards like Jo Grant that trigger whenever you cycle. Also, since discarding the card is the cost and the tutoring is the ability, any abilities that trigger when you discard a card like Inti, Seneschal of the Sun trigger and resolve after you discard the card but before you search your library
For example, Jacked Rabbit creates 1/1 white Rabbits equal to its power everytime it attacks and if you happen to have used Offspring on Jacked Rabbit as you cast it, your Offspring will create an additional white Rabbit token every time either one of them attacks
While its a bunmer that they sloce the plastic on the box, I whole heartedly support the decision especially when people seem to be buying boxes in bulk because scalpers suck, while I can see the potential annoyance at having a box 'opened' if you're buying a single box in the long run its such a minor issue