Can we mark DataCon ptrs only in allocation sites and not generate entry code?

As far as I can see in the native code compiler we mark DataCon pointers in two places: 1. In allocation sites (StgCmmCon.hs:240) 2. In DataCon entry code (StgCmm.hs:244) I was wondering why we can't get away with just doing (1). Can anyone give me an example where an allocation doesn't return a tagged pointer and we need to tag it in entry code? If every allocation returns a tagged pointer, then why do we need (2) ? Thanks