The reasons LAs prefer TEACCH to ABA imho are a) cost and b) prejudice, and old uninformed views of ABA as "cruel" or "intense". By the way, it always amazes me that LAs will say that ABA is "very intensive" and will mean that as a criticism. When my son was 2/3 he couldn't :
talk
understand anything said to him
play
Use toilet
dress himself, or even know what dressing himself meant
make eye contact
play with anyone rather than just alone
stop jumping up and down on the spot screeching "eeeeee " and flapping his hands, for more than one second, or when asleep
understand any dangers at all (cars, electricity, water, heights, windows)
read
stop flooding the houseby running taps constantly
bite anyone who annoyed him or headbutt them.
With that list in mind, I think an intensive approach was a good thing, not bad.
The patronising, paternalistic attitude to SEN nowadays goes something like this
"we're not allowed to discriminate against the disabled nowadays. So surely it must be discriminatory to try and change them. If that little boy wants to spend his whole day licking the window, that's his right. Any nasty people who try and change him are anti-disabled or some kind of fascists. That's what ABA is like"
Of course they would never articulate it like that, but that's the root feeling.
ABA has been the absolute making of my son , and the sons of very many of my pals with autistic kids.
I am not without experience of other methods, having paid out £1000s on TEACCH and traditional SALt as well. To zero effect.
I suppose the interesting question is - are there any people out there who have done ABA and had zero good effects? Because the anti bigade do, as Starlight said, seem to consist largely of those who have no personal experience of ABA, but have heard it's bad. Good luck with your essay!