While that may be possible for some, only God knows..and I would think saying they left church because they never were of the faith(meaning every single one of those who left,this pertains to them) is a bit of a broad blanket statement. Having said all this..I will appeal that there are scriptures in romans 11:16-22,1 timothy 4:1,Hebrews 10:26-30,hebrews6:4-8,hebrews3:14,2 timothy4:4..are several scriptures that prove that apostasy is possible. My issue with an adherance to what many call here OSAS aka eternal security is that it creates a spiritual sluggard, lazy sunday christians who are more interested in being confessional then actually repenting and changing their lives. Why not go the extreme of OSAS and keep on sinning? I say this because i have met many who adhere to OSAS and do not have any fruit in their lives,and downplay the importance of repentance. Sin is made not a big deal too according to OSAS.