Why does this app even exist?

I dont have space on my phone for an app that serves no purpose. If my Facebook friends want to say something they can just post to my wall. If they want it to be private they shouldnt be doing it through Facebook in the first place, thats what email/text/phones are for. There is no way to disable messages so even if I dont download the app people can still send me messages not knowing that I will never see them.

Mimijump2 about Messenger, v128.0