737NG Grammar Question

I noticed that the grammar for SID (SID NAME sidstarrunway sidstarrunways fixlist) differs from that of STAR (STAR NAME fixlist sidstarrunways).The critical difference is that the SID requires at least one runway to be associated with the SID NAME whereas the STAR requires zero or more runways. Was this by intent? And what is the corresponding interpretation: For example in the case of a SID that applies to all runways I am obligated to list them all (because I must specify at least one runway). But for a STAR that applies to all runways it appears that I can do so by omission OR by inclusion of all the runways (What other meaning could there be for a STAR with no runways specified?)Just curious.Thanks.-michael