Shel90, I know what you are getting at in terms of it being something a deaf child can physically do, and I agree with that. But unfortunately, in practical application, ASL is not accessible in many environments and to many families that have no connection to Deaf culture. It's not taught as a second language in most schools and colleges (across all of the Harvard Schools, it's ridiculous, but there's not even one ASL class), and aside from schools for the deaf, which are dwindling in number, there are few teachers available in public or private schools with ASL skills. ASL instructors -- good ones -- are few and far between, most often you get someone who learned ASL as an adult and is far from fluent.
To provide my child with an ASL immersive environment, I've got to argue a need for ASL, despite her ability to test into a mainstream environment without accommodation (and we all know that testing is very different from real life application), I've got to make our case against the two auditory / oral focused schools for the deaf within a hour of our home, swing the $55-60k annual tuition/transport cost with the help of our state/local school district, and a put my child on a van for 4 hours a day. We can't leave our home, our jobs (I can't afford to go part time to spend more time with my child), or we forfeit an arrangement we consider to be the best possible educational environment for Li-Li.
And I'm lucky in that this is possible for us, that this wonderful school is -- though far -- still within reach, that our administrators are in favor of this, and we have the resources in our state and at home to make it happen. I've spoken with many parents for whom there's just no option to include ASL, and for their children, ASL is about as accessible as Tagalog is in the US: similar # of speakers/users, places exist with high concentrations of native speaking population, but very sparse in most places. And even if your child (and hopefully your immediately family) becomes fluent in Tagalog (or ASL) there's still a language barrier with extended family, friends, and people you encounter in everyday life.
I'm invested in making certain my daughter communicates as fluidly with ASL as with spoken English, but it's by far more difficult for us to make that possible than it is to provide English immersion.