They are afraid that people will look back at a time when their lives were simpler. They were worldly, didn't have to worry about boasting sessions and field circus, and actually had some fun. And now, their lives are a hassle, a drudgery--for nothing. This is so blatant that I didn't even need the stock examples they put out from the LIE-ble to back it up. Of course, it is worthless advice for those who were born into the cancer.
However, that advice is soon going to come back to burn them. For those who were born into the cancer and are now of age, anyone with a computer should be able to do research on the religion and see what a scam it is. At which point, they are as likely to leave the cancer and not look back. Especially now, with Aquarian pressures to do more research and question everything added to the temptation already present, people are going to see what rubbish Christi-SCAM-ity (especially so the witlesses) is, and ditch it altogether and not look back.