The terrazzo in my building has a tar paper vapor moisture barrier between the...

[darkertint]

...terrazzo and the concrete slab.? The terrazzo in my building (healthcare center) has a tar paper vapor moisture barrier between the terrazzo and the concrete slab. Why was the vapor barrier used here, but is not used normally with terrazzo? Is it to help prevent cracking? Is using a vapor barrier part of an industry standard terrazo installation?