To make chat messages easier to control. Other online games have simple but effective chats that allow us to have different tabs open. SK just mashes it all together in a way that you're forced to do a silly amount of scrolling to see someone's /whisper if you happen to be in a crowded Haven and you're also in the /trade chat :I
P.S: I dunno if this has been suggested already. I checked the first three pages of the Suggestions forum to see if there was something similar. Since I didn't notice it and I don't want to gravedig an older thread, I made this one.
This has been suggested before.
But I still support it.