Where do you get this stuff? Did your preacher tell you this one sunny Sunday morning?
No.
It’s logical.
If you believe the Book of Mormon and what it preaches, wouldn’t you want to live under the “law” and the life as described in that book?
If not, are then you would have to ask yourself if you are a Mormon.
Because I am a Christian, I read the Holy Bible, agree with its law and the life it describes, and I strive to live under that law and live that life as close as humanly possible. This is part of my walk with Christ. To NOT do this, would mean I am not a Christian.