It's much easier to label buttons when you work for a small company, because you know exactly who does what and exactly who is responsible for labelling the buttons and you know exactly what's going to happen to you when you label them, so you just do it and have that debate whenever it happens. Bystander effect, etc.
It's true but that falls more into the explanation-not-excuse category. I bet there's someone advocating for better ad partner integration and driving projects for that - no reason they can't have it for UX/UI/Accessibility too.
