I mean, video games don't necessarily have to include an overarching plot. Plenty do, and plenty don't.
Video games are sort of the birthplace of the "excuse plot," which is that threadbare bookend plot that justifies why the game is happening at all. Something bad happens, then the video game occurs, and then the bad thing is resolved. Or there's Ultima 4, where "something bad" is just replaced with this abstract goal, and then the game happens, and then the goal is resolved. Somewhat more modern games of the kind will usually include story development or a plot twist in the middle. It's not exactly traditional literature and it's not exactly great storytelling.
The idea sorta was that the gameplay was the reason to play the game. Our transition into the most modern story-loaded games (VNs at the extreme story end of that) sorta smears out the tradeoff between story and gameplay. So nowadays we have all different kinds of gamers, some of whom are looking for a story, some of whom just want to play a fun game, and some of whom are somewhere in the middle. The middle folks might be okay with characters that they like interacting with each other in enjoyable ways, rather than some kind of overarching story that involves those characters.
I mean, if you get really nitpicky about it, pretty much every game's gameplay is a conflict between the player and the game. The player wants to see the ending graphics, or get the satisfaction of some kind of accomplishment, and the game's there to make that difficult for them. So, yeah, even if there's no in-story conflict, there'll usually end up being some kind of conflict somewhere--otherwise there's nothing really there.
And yet, having said that, there are a few exploration type games where there's no conflict except maybe obstacles preventing the player from getting to some neat thing or place. That kind of thing slews pretty close to a "games as art" idea, or an interactive experience rather than a traditional video game.
If a game has a traditional plot, then yeah it's going to have traditional conflict, because that's sorta how a plot's defined. Video games don't necessarily need a traditional plot. Heck, modern entertainment and not just video games have kinda moved out of the realm of the necessity of traditional storytelling. Look at something like the SCP project, which is basically a collaboratively-developed fictional encyclopedia. It's not wildly popular, and it's not something everyone's going to enjoy, but the Internet's kinda made it possible for even marginally popular things to find a fanbase. I guess porn gaming's the same way: if there're enough people out there who enjoy storytelling paradigm X with breasts added, you might just be able to get enough of them together to be successful.