Of course not, but if the player is presented with that kind of a choice, then the path to getting cheated on involves being an asshole that refuses to spend time with his gf. Obviously, such binary thinking is a far cry from the reality of dating, but in the context of an AVN, it's a decision that negatively impacts your relationship. UNLESS the decision to stay home brings with it a different kind of reward or advantage for the player, you are essentially purposefully being an asshole (within the context of the game) to get on the cheating path.
For example: Mel asks the MC out to a walk. The MC is given two options:
- Join Mel for a nice time (+points for a Love/Faithful relationship) but you antagonize Ben/Dave/Boss by foregoing your responsibilities for your gf, meaning they are more likely to go after Mel in "revenge".
- Stay home and work on the project (+points for Sharing/Cheating) but you gain more money/ideas that you can later use to buy an expensive gift for Mel - that will then give you points towards a Love/Faithful relationship.
In this scenario, not accompanying Mel could lead to her coming across Ben or Dave, and instead slowly getting closer to them but the MC later still has a chance to grow closer to Mel with the aforementioned gift.
This is just one example of a very forward-thinking decision pathing that could immerse the player more into each individual route, but of course, not all decisions need to be designed like this; each having it's own reward, but having some side-effects that make the MC think about their choice beyond the simple surface.