No, it doesn't, but we don't include an e-mail client and an image processing software, either. Everything in this world that's done properly is like that because it focuses on doing one thing right, instead of ten million things half-assed.
As has already been stated, its simply much more convenient for it to be all in one place. You don't need a fancy system created, nor is anyone asking for that. Simply a message that instead of being a message, is stored as a note. I have no idea how notetaking systems work so I can't say I know if its a lot of work or a little.
Why to not have an e-mail client? Because it has nothing to do with the game/doesn't help the game at all. Why to not have an image processing software? Lots of work, and little use/reward. Why to have a notepad with characters? Because its convenient for all players, will likely be used by nearly all players if they don't use a separate note service for BM, and has a lot of reward to it.
