In addition to giving a nice 4-life tax to prevent opponents from targeting you or your stuff, it allows opponents to copy a spell whenever you copy one
Set completion particularly benefits players focusing on Standard formats
They typically say something along the lines of whenever you draw a card and there are even cards that care about when you draw your second card each turn but those get their own list and you absolutely should read it after this one
I headed down for the launch and found that the system worked
Mega Zeraora ex, Special Illustration Rare (#114)
Standard, for example, warps around outliers like overtuned mythics, pushed synergies, or singularly efficient threats, crowding out metagame choices incapable of competing at that level