The point of Neurath's "ship of knowledge" metaphor is that
We can never examine all of our beliefs at once, as Descartes would have us do.
We are always "out to sea" and can never dry dock.
What was once a good ship becomes leaky and unsound as science advances.
We need new ships to keep up with new learning.
Your knowledge base becomes ever more seaworthy with more education,
especially in the sciences.
People naturally want to float around like minded ships, preferring an armada of
similar views to bolster their worldview.