Many times during a game a button has one function. Left click to attack, right to block. They have these functions, and to not confuse the player, they keep it that way. To minimize the amount of buttons used in a game, a action button is often introduced. This is a button which is used for several purposes. Opening doors, opening chests, talk to people, etc. This is a nice way to tell the player that this is the go-to button for interacting with objects.
ArcaniA's interaction button has multiple functionalities that encourage exploring and makes it simple to interact with the world. Some of the functionalities are sitting on a bench, sleep in bed, loot, brew elixir and talk with people.
Interacting with elixir table.