How about this:
It was very tedious to manually play through 3 gw on this day before. With the simmable gw, more and more players would do it, meaning more guilds were hitting maximum rewards on that day.
The game economy is delicately balanced to the point where the additional guild currency being earned was out of whack with what the developers intended, hence the change.
Obviously as players we want more currencies all the time, but the development team has a different vision for what “optimal” looks like than the players do.
I don’t see it as a money making play. I don’t know many guilds who push the daily activity to maximize guild income as it’s just too much effort to track. We ignore it almost entirely and just push the daily 600, knowing that we will get some guild currency along with that.