I think the author's perspective is skewed because he's living in Yogya, which is, and has been for a long time, the center of a large and prestigious culture. Yogyakartans don't need to speak Indonesian unless they're dealing with the government.
It's very different if your native language is only spoken by a small number of people and / or isn't very prestigious.
Then there is, like you said, the capital, Jakarta, where non-Indonesian languages are only spoken at home (or not at all).
And I know for a fact there are is at least one region - but there's probably more - where the local language has pretty much died out. Minahasans, from Northen Sulawesi, no longer speak Minahasan languages, they speak Indonesian.
It's very different if your native language is only spoken by a small number of people and / or isn't very prestigious.
Then there is, like you said, the capital, Jakarta, where non-Indonesian languages are only spoken at home (or not at all).
And I know for a fact there are is at least one region - but there's probably more - where the local language has pretty much died out. Minahasans, from Northen Sulawesi, no longer speak Minahasan languages, they speak Indonesian.