MOBA games in general have a PvE element to them, with the idea of having creeps and a jungle in League of Legends, DOTA2 and etc. These games even introduce an entirely PvE mode sometimes. Smite introduced PvE modes like Xing Tian’s Mountain and Fafnir’s Wonderland, and League of Legends introduced Doombots.
Even an FPS like Titanfall has introduced PvE elements with the inclusion of bots for players to kill in a PvP match.
So what is the point of having all of these PvE elements in a PvP game? Well first we can take a look at the reverse case.
When it comes down to big multiplayer games one of the memorable genres would have to be the Massively Multiplayer Role-playing Games or MMORPGs, such as World of Warcraft.
These games were the reverse of what most multiplayer games would be seen as today, a largely PvE experience with some PvP aspects littered about. Having PvE in an MMORPG is the norm and PvP is usually seen as an extra thing added in at the end game.
So what is the point of PvP in a mostly PvE experience?
Variance.
By introducing PvP into a mostly PvE experience, developers give player something else to do. There are players who only do PvE, and there are players who focus on PvP. By introducing a PvP element it gives players a choice.
For example, in World of Warcraft you choose between a PvP server or a PvE server. In a PvE server you never have to worry about being killed by other players and you can just go do PvE.
However, if you choose a PvP server there is a chance of you being killed by other players. Some might not enjoy this sort of thing but there have been memorable moments for players in WoW where there were full blown faction wars which happened by chance.
Many people love this instability and variance in their games.
So what is the point of PvE in a mostly PvP experience?
Stability.
Much of PvE is something that players can learn and calculate. Many people love the fact that things might not ever change but because of that they can constantly fine tune their skills because of the lack of variance.
In a MOBA the minions moving down a lane are a PvE element, and in League of Legends last hitting (getting the last hit in for a kill) the minion gives you gold. Some players learn and ingrain upon themselves how to control waves of minions, how much damage they need to clear a wave or even just how to last hit effectively.Many players prefer to go for the PvP and kill people but some players enjoy being able to master their ability to last hit and control a wave.
Like with the minions in League of Legends, Titanfall players could just kill bots even if they weren’t skilled enough to kill other players. This was an aspect of Titanfall that allowed lesser skilled players to contribute to the team.
In the PvE modes of Smite and League of Legends, many players enjoyed the experience of just being able to see just how far they could get against Ai controlled opponents.
Like PvP in a PvE experience, PvE in a PvP experience brings variance and variety.
Some gamers are fine with playing the same mode while others ask for different content.
By adding PvE elements into a PvP experience developers can give players more things to do, and reach new players that might never have touched their games to begin with.
