Abortion isn't a black issue, there is also the matter of the debate of what constitutes life. There are absolutely people within the black lives matter movement who have differing opinions on abortion.
Now as far as what the emphasis is or should be, who cares? Police brutality, black on black crime, mass incarceration, educational funding inequities, etc. are all symptoms of the disease. It's more convenient for you and others like you to focus on the symptoms when the focus of the disease needs to be the cure.
Finally please don't tell me what the focus of the movement is, trust me, I know more about this than whatever representation of us you may see in the media. You seeing signs at protests when a cop kills someone isn't close to the totality of what this movement means. If you are sincere about knowing about this heed what I'm telling you because I'm a much better source than whatever else you're reading.