I have used Google Maps for public transport very actively in multiple cities around the world, and I can't imagine living without it. Stockholm, Singapore, London, Tokyo all have it with Google. And I'd bet that a majority of smartphone users in the world use public transport, not cars, as primary method of getting around.
The people for whom this is a big issue are a fairly small proportion of the global population. Basically those in the US who live in major cities and are users of the transit system. In San Diego and New York this is a big issue and those are centres of the HN readership and probably also the tech media which might be important but the practical impact of this limitation may be limited.