Feeling obligated to return a favor, share resources, trade an item, etc.
"The game encourages you to send lives to your friends and ask friends for additional lives."
"You can request a type of material from your club once every six hours."
"Not really but you unlock special traits with yout team if you play frequently."
"lets you upgrade a pet that you can combine with other peoples pets to share your upgrades"
"There is market box system where you can share items with your friends, encouraging players to pick and share certain fruit to share with friends."