Assassin’s Creed 3 lets you pet dogs. Asheron’s Call lets you tip cows (and even added a quest for it). Guild Wars 2 uses some animal and NPC interactions for its hearts, such as feeding cows or watering crops.
Every now and again, it’s nice to have options other than “kill them,” you know? You may not spend much time tipping cows or petting dogs, but just knowing the option is there makes the game a bit less of a murder simulator.
Every time I see the abbreviation for Assassin’s Creed 3, I think, “They’re making Asheron’s Call 3?!?!!”