I cannot answer this without including some spiritual thinking. May be you will never understand this also.

Both scenarios happen because of lack of PERSONAL integrity & / Or lack of FAITH in a higher being or the Karma Effect. If either of it was there, this situations would be avoided by the person.

Now, all scriptures of every religion says, GOD knows everything. If you truly have faith in your scripture, then knowing that what you are doing is known to HIM, will you do it ?

That happens because of ignorance about why are we having this human birth. The lack of knowledge that we have many births and which living form we will obtain in the future will be decided by our present karma (Actions ) in this birth. When you believe that you only live once, you tend to care less.

Google - Near Death Experiences & Real life Reincarnation stories

We are not understanding that we are in the process of evolution. we are to refine ourselves each day with our knowledge and thereby decision making, to attain a higher self. If we fail in that, we go down the path in evolution - in our subsequent lives.

We are all in a false ego that we are just our body and this mind, whereby we are very intelligent and can control everything. But we are not trying to understand how " Life plays against us " and we will be coming back here again and again to pay the price for it. Think, why someone is born rich and some in Africa without even proper food.