some ppl ask why would God let the Hitler kill that many ppl?
I ask do you think that will ever happen again?
so wouldn't this make it better for humanity?
It has to do with free will. If free will is to be truly free, it will need to have complete choice over all alternatives. If you could only do good, you would not have free will.
The question should be, why is free will so important, such that even evil and atrocity will be allowed, since there are all free will options?
Say we had a supercomputer, through which we hope to achieve AI or artificial intelligence. As long as the computer runs smootly and perfectly, it is just a super computer. If it suddenly started to mess up in odd ways, this might signal the start of AI. We will first notice AI, via its departure from the rountine programmed perfection. It is easier to break than build so free will have to crawl first and will break something. Say the little AI starts to get every calculation wrong by exactly 5, this can be very annoying to everyone using the computer, but it tells us it has become free. This is bad at the level of perfection and all those people who depend in this computer, but good at the level of AI autonomy.
This calculation bad, is good in the short term, since it signals free will. The annoying mistakes are evidence of its budding free will. But eventually AI free will have to be more than a negative/contrary one trick pony. if you say left it goes right. The next step in its evolution is, uit has to use that freedom of choice to freely choose perfection; fix the mess created.
If the supercomputer, that first shows its free will, by screwing up, can only screw up, it will be unplugged, since this type of free will wears thin. In the short term even this bad is useful. But in the longer term, the AI needs to take the next step, like fix all the errors in the calculations and then start to reprogram the computer for the better.