I'm interested why top game companies put a lot of "background" animations in their games - has it been demonstrated to increase user engagement? Does it take longer for a user to get bored of a game with background animations vs the same game without background animation?
I'm looking at a couple examples of relatively static game Heartstone (card game) for PC and a top selling game "Clash of Clans" for iPad. These aren't action games, and consist of a player moving pieces around every few seconds. The focus is on the piece being currently moved. I noticed that Clash of Clans uses a lot of minor animations of characters walking around, just about every building is either glittering or bubbling or otherwise plays a small animation every few seconds. Even my cat notices that when looking at an iPad:
Heartstone is another game by a major company which also uses animations - For example in the image below, the griffon head is turning, some flags are waving and the windows of the houses flash. These are non-playable elements.