that’s because和that’s why 有什么区别?

that's becoz后接某事发生的原因
that's why后接某事产生的结果
如,
i was late for the appointment.That's becoz i met with an old friend on the way.我约会迟到了,因为我在路上碰到一位老朋友
i met with an old friend on the way,and that's why i was late for the appointment.我在路上碰到一位老朋友,因此我约会迟到了