Use of Multiplayer increases uncertainty and therefore engagement Many games suffer from a lack of compelling narrative, or a strong single player mechanic. But many of them make up for such problems by creating a strong multiplayer mechanic. A well balanced multiplayer allows for a great deal of uncertainty due to the existence of other equally matched players, keeping the players engaged.
BattleField 4 Edit
The Battlefield games have a long history of forgoing long campaigns and favoring multiplayer engagement instead. They avoid lengthy development cycles required to make compelling story modes, and focus instead on the aspects of the game that keeps players playing.
The Dota gameplay is fully dependent on the multiplayer strategies and how the player moves in order to tackle the other player in the game. The game mechanics changes according to each players strategy and most of the time the players need to communicate with each other to build those strategies.
Each player must analyse opponent strategy and decide the best outcome for himself and the team at that particular moment of time. So for this each player has certain task in mind which they will play and coordinate with other players as well. This increases uncertainty since each player doesn't know what move the opponent will perform but at the same creates a strong multiplayer experience for the players.