As someone who helps manage the clan I am part of, it would be easier to keep track of who is participating in group events like raids etc when they are online. Often times we'll post in clan chat about helping with raids and it will be ignored. We know people are online cuz they they are helping with builds etc, but it would be easier to pinpoint who is online and who isn't so we can decide weather or not to remove them for non participation.
R4 and R5 clan members can see other members' online status. It'll also tell how long it's been since an offline member last logged on.
Non participation in raids? I feel like we have to run 3 a day lvl3s to let everyone that wants raids get in on them. Maybe it's that the lvl3s give so many rewards compared to the lower ones.