Limited time offers with unnecessary urgency.
"Seasonal decorations in exchange for points you gain for completing orders - they sell discounted bundles for energy and diamonds so you can keep playing and collect these decorations"
"The game might offer energy bundles at a discount for 10-15 minutes after you've run out."
"There are many seasonal events that you have to play constantly to finish."
"the game is always running special events that add cosmetics and new levels to the game. the cosmetics can only be purchased while the event is active and the levels cannot be purchased, only playable while the event is active. sometimes they offer brief limited time offers on their valuable boosts"
"There are daily offers and bundles. There are also events, but these are seasonal and come back every year."