In game design, Realism is a tool, not a goal.
Realism serves multiple purposes:
- Intuitive design. E.g. No need to explain that: drink more -> more going to the toilet
- Humor. Reality sets expectations, which can be exploited for humor. E.g. break the 4th wall.
- Advertisement. Many players are excited by the idea of simulating something. E.g. Kerbal.
- Educational, similar to the above. Some players and many parents/teachers are excited by games that promise to teach something. E.g. Kerbal.
If I have to mention just one thing about realism that people hateplayers don't respond well to, it is excessive negative repercussions for events/actions outside of the player's control - imagine a 3D shooter where occasionally the player gets a heart attack and needs to start over from the beginning.