The argument for why God doesn't just take everyone to heaven is that He gave humans free will. He wants people to choose to love Him, and doesn't want to force anyone to love Him. He doesn't want robots.
I can understand the not wanting to force people to love Him. I don't get the not wanting robots part. The whole reason for Jesus as a Savior is because God is a Holy God, and can only tolerate perfection. People are not perfect in any sense, having inherited the Adam nature. Depending on how far one's theology takes this, everything you do is tainted with sin, no matter how "good" it is. As a penalty for the sin and disobedience, Jesus took on humanity's punishment, thus satisfying the wrath of God.
If God can only tolerate perfection, and sin is essentially going against God or some form of disobeying God, and thus God can only tolerate sinless creatures (for those are the perfect creatures) and the only way to be sinless is to do exactly what God wants ... isn't the thing that God wants the same as a robot? Someone who does exactly what He wants?
Because that's exactly what a robot is: it's something that does exactly what the creator commands.
And then if the robot does not behave as the creator commands, it is declared defective, and is either fixed, or trashed. Perhaps melted down in a burning fire, and thrown into the scrap heap.