I assume that those who have rejected an invite will still be visible there, and the list may include players who have been accepted to your CC or to another CC. Thus it seems clear that some necessary maintenance and cross-check is NOT done by WGT.
OTOH, would you like to have players as members who didn't respond in weeks or more?
Last but not least, the pendings are on the list for all to see. Owners have received criticism by the public in multiple cases when their CC came into discussion here. Thus, owners better delete the dead wood for a "clean" history.