The Galaxy S8 will have an extra button dedicated for Bixby. Originally it was reported that the button could be reprogrammed to launch other apps, as well, but apparently that's not the case. That button belongs to Bixby, and just who do you think you are trying to give Bixby's button away?
Users were hoping that they could use Android's built-in Accessibility Services to "intercept" the Bixby button's command and change its function, but the Galaxy S8 system firmware makes that impossible.
Now, to be fair, this is Samsung's phone. And the way Bixby is shaping up, if we could get around using it, we almost certainly would. They want to make sure that their new assistant has a fighting chance, and making it a permanent fixture of their new phone certainly does that. Unfortunately, for some consumers out there, it might make the phone a lot less appealing.