reincarnation

i like the idea of reincarnation because it evens out the seeming inequality that is our earth life.
if this earth life is meant as a sort of test, trial, or growth experience, how can it be a fair one if some people are born into middle class devoutly religious homes, have high i.q.'s and mild temperaments with parents who are loving, tolerant etc. and some people are born to drug addicted, abusing, with no opportunity for an education etc homes.
some people only live five years while others live 120. some are even aborted or miscarried fetuses.
if such a wide range of experiences exist, how could this be any sort of a just test or trial. why even bother having such a test.
but if people are being born again and again, it seems the inequality would end up smoothing itself out. people would get the opportunity to have all variety of experience.