Some reasons why people breakup are: they fall out of love; one has cheated on the other or both have cheated on each other; one of the two people involved in the relationship may use too many street drugs; drink too much; have a criminal record and end up in prison; financial stresses; flirting too much; jealousy; mental instability (mental disorders); health issues; unexpected pregnancy and the young man deserts his partner or, sometimes the young woman may be the one to desert her partner if she is pregnant. These are but a few reasons, but the most popular reasons.