You might as well have asked why the father didn’t just prevent his wayward son from leaving the house, why the shepherd couldn’t have just taken measures to prevent that one sheep from straying the herd, why someone would ever get the idea to build his house on sand, why the Samaritan didn’t just pay the innkeeper then and there, why the sower couldn’t have just sown the seeds more properly, or why that one guy got such a disproportionate treatment when he simply hadn’t followed the dress code at the wedding feast.
The point is: they’re stories told to make a point. There’s that whole ‘suspension of disbelief’ thing at play here: they don’t need to be ‘logical’ or ‘plausible’ in order to work - I’d say even that they
shouldn’t be ‘logical’ or ‘plausible’ in order to work. After all, the point is what’s important - the story is just an illustration to convey it. Suspension of disbelief is actually essential for
any kind of storytelling, I’d say.