With more players playing Splinterlands, I have been observing that my daily quest rewards have started to include more DEC and potions loot and less cards in the rewards.
If there are cards, it is either a Harvester, Nightmare or Ant Miner. My theory is that the rewards cards are getting spread around more players making them even rarer than they usually are.
Ultimately, there are only a fixed number of cards that go into print and if there are more players playing now, then it stands to reason that there will be fewer rewards cards per player going around before they eventually run out.