- You want to destroy humanity in a 100 years
- You dislike your gahmen and foresee that they will not change in the near future
- Your career is unstable
- Your parent is poor(means they have to work at old age and cannot help to take care your children)
- You are not very well education. Gene is very important, we got to breed elite
Other than the above reason, you might also consider staying single if, your workplace is too far from home; your work is stressful; you want to save your money for yourself. Etc, etc.
I think you can find more