We have the freedom to choose, therefore we also choose to be reincarnated. So why do some people choose to be born in families in poverty stricken areas e.g.: most of Africa where most have no or little opportunity to have a decent quality of life?
There is no guarantee that what you called "a decent quality of life" is the best situation to learn to live.
From my own perspective, I have learnt the most when I suffered. One of the fundamental traits of the human Nature is that when we don't have to - we don't make enough efforts to THINK, learn and understand.
When people live comfortably - it is VERY difficult for them to understand suffering and poverty. It is very easy to avoid thinking about reasons and consequences of suffering and poverty. Most people prefer to PROTECT their comfort rather than help those who suffer. There are so many temptations to AVOID thinking about the Purpose of Conscious existence...
Perhaps those who choose a "hard life" have failed to attain conscious progress they were aiming for, when they had an opportunity to live comfortably.