If you don't give unit with your magnitude (number) then, anyone can't figure it what you are talking about!
Suppose, you said, the weight of an iron bar is 10.
What does that mean? We can't even figure out how heavier is it.
Now, If you tell that the weight of a person is 10 Newton, then it makes sense 'cause 10 N has specific value. When you wrote 10 then, it could be newton, dyne or any other derived unit.
Hope this helps!
