Luke 8:13, "They on the rock are they, which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away."Scripture says that they do believe, but only for a while. They are never born again, they just taste the heavenly gift (Heb 6), they don't eat the bread of life. Matthew 13:21 explains why they fall away:"Yet hath he not root in himself, but dureth for a while: for when tribulation or persecution ariseth because of the word, by and by he is offended."These are they that see what happens to the man who picks up his cross, and see the fact that he isn't coming back, and want no part of the promised temptation, tribulation, and persecution. They may even stay in church, but are not one of those "born-again Christians."