I’ve not had experience with this in the US, so that may be true there. But in my experience elsewhere, it’s not about the quality of the data (as you say, everyone’s using essentially get same data feeds), but the quality of its presentation and context.
Apple & Google Maps are general purpose and have to use a one-size-fits-all model. So they can’t design it around the peculiarities of a local transport network or information that is particularly important. Your experience of last bus times is a good example of that. I’ve just found that local apps tend to present the options more clearly and have more useful ancillary information.
As to the issue of resources, while Apple & Google certainly have more, public transport is a small part of what they’re trying to do, and it can be neglected compared to developers who are focused only on making public transport routing as good as it can be. (In the case of Apple & Google, the public transport part also has to fit into the overall design of an app which seems designed for and focused primarily on driving directions.) So it’s not always an issue of total resources available. I’m not saying that all local apps are better or discounting your experience in the US. Just that I think there are reasons why it can also be the reverse elsewhere.