Uh; because they had no assurance of salvation??
Since cut-and-paste of dueling scripture isn’t leading us anywhere, how about taking a step back to look at what made Purgatory needful? It’s tied in to infant baptism.
The early princes of the church believed baptism was necessary to achieve heaven at death. So infant baptism was instilled to cover that base. All was well, for a while.
Then some over-thinking malcontent decided that while sin was sin, sinning in a state of post-baptismal grace was more sinful than sinning unredeemed. What to do?
Well, it was pretty obvious. Hold off on baptism until you can get your sinning in and get baptized just before dying. All was well, for a while.
Then some prince fell off his horse, hit his head on a rock, and died unbaptized. Yikes. What to do?
Then a pragmatic believer convinced the other princes to invent a space where post-baptismal sins could be worked off. Sort of a celestial chain gang.
Say hello to Purgatory.