Standard for Interconecting DG in EPS

it's about "standard for interconnecting Distributed resources in electrical power system"

on of statements i've read " DG shall not actively regulate the voltage at the PCC (point of common couple)" i quote it from IEEE1547

sounds like DG act more like PQ-bus in AC system..

why it should be ?? and if this interconnection could improve power quality for voltage profile improvement, WHY NOT..??

i hope electricians and all the Guru in this forum are willing to make me clear about this ambiguous statement...

thanks a lot and regards