That's because we are all created as volitional beings. That's part of our human nature. We must willingly believe in Christ or else it's a sham. God is not fooled. The calvinist idea of be inert, do nothing, and wait for the zapping is a sham at best.That doesn't address the reason why some believe and others don't. My point to @synergy was that if you believe this:
God's will is to save all without exception.
But God doesn't save all without exception, he leaves it up to you.
So you're ok with people being dragged kicking and screaming into Heaven? Calvinists are certainly a strange lot.That places man's will above God's will. It's an impotent god who wants to save everyone but is unable to do so because man won't let him.
The real God wants our wills to be conformed to His will.So you're stuck with two possible conclusions: Either your god is impotent, or the real God doesn't want to save all without exception.
(Luke 22:42) saying, Father, if You are willing, remove this cup from Me. Yet not My will, but Yours be done.
(Rev 22:17) And the Spirit and the bride say, Come! And let the one hearing say, Come! And let the one who is thirsty come. And he willing, let him take of the Water of Life freely.