The short honest answer is that we do not know precisely.

Some ochre at Neanderthal sites appears in association with stone tools and may have been used for practical purposes — certain forms of ochre can be used to bind adhesives, which would be useful for hafting stone tools to wooden handles.

This is a functional explanation that does not require symbolic cognition.

But ochre has also been found in contexts that are harder to explain purely functionally.

At sites like Maastricht-Belvédère in the Netherlands, ochre was present without obvious practical correlates.