With the Galaxy Note 9, Samsung decided to remove the option to disable the dedicated Bixby button on the device. This caused a lot of negative feedback from reviewers and everyday users of the Galaxy Note 9. Because of this, Samsung has decided that it will be bringing this option back to the Galaxy Note 9, and it expects it to be available via an update by the end of the month.
Bixby is Samsung's own personal assistant, that it debuted on the Galaxy S8 last year. Since the Galaxy S8, it has had its own dedicated button on the side of the phone. This is cool in theory, as you could easily pull up Bixby and ask it to do things, etc. However, many are finding that they are pressing the button by mistake, time and time again. Which causes Bixby to open when the user doesn't want it too. Hence why they want it to be disabled so that they aren't pressing it by mistake all the time. Some users would also like it to be remappable, so that you can use it to open up the Google Assistant (a la the LG G7 ThinQ), or even use it as a dedicated camera button, which many people would really appreciate.
It's still unclear why Samsung decided to remove the option to disable Bixby on the Galaxy Note 9, seeing as the company had added it shortly after the Galaxy S8 launched, and it remained until the Galaxy Note 9. Perhaps, since it was debuting Bixby 2.0 with the Galaxy Note 9, Samsung thought that more people would want to use Bixby. But the actuality here is that Bixby is still a pretty hot mess, compared to other personal assistants on the market right now - like Amazon Alexa and Google Assistant. The update should arrive by the end of the month, to disable Bixby. Though in the US, it may be a bit later on.