There are countless ways to reach out to Bengali speakers, only one of which is the Indian government - whatever politics governments may play, a technocratic institution should be focused on getting things correct.
Did you know that the Indian Government has a department for just such a thing, http://tdil.mit.gov.in/ ? What has it been doing all these years?
Added later: there's also CDAC http://cdac.in/index.aspx?id=mlingual . And these are just 2 that I found quickly.
The fact that it is their goal to set the standard for the textual representation of human speech means that they take on that responsibility.
<s>Why is Wikipedia not doing more to translate the 4.7M articles into Bengali? It does claim to be the world's encyclopedia!</s>
Unicode on the other hand is the only way many people have to input and see text in their native language. When one group proposes being the ultimate solution to everyone's problems, and then pushes their standard forward as such, complaints about inadequacies in the solution presented are perfectly fair and valid.
There's no point in taking on a job and then declaring it to be too difficult.