There is, and will always be, a gap between what is strictly allowed/legal, and what is considered ethical/courteous.

There's a number of things that are strictly speaking legal, but still considered rude. Often, the reputation of a person or business is based at least in part on whether they do the legal bare minimum, or if they hold themselves to some level of higher standard.

I also think there's a difference between attribution because a license requires it (commonly buried several links/pages deep in some obscure "Here's a laundry list of ALL the open source packages we used to build this"), and acknowledging that a _specific_ library powers the core of a new product. I don't know of any license that marks that line.