No because the official OSM tile layer is heavily subsidized by Fastly (€720k last I checked) and rendering by AWS (€40k)
Yes because technically it would use fewer resources thus easier on AWS+Fastly and also easier to self-host
In last risk assessment I read closely(1) OSM noted "If we lost [Fastly] sponsorship, we would likely cut off all third-party access to the standard tile layer and run a small number of Varnish servers."
As I understand it, primary drivers for vectors was not cost more improving internationalization, generally enabling client-side rendering decisions, and driving a modern toolchain that would net multiple follow-on benefits
I'm a bit behind, there is more recent info available at (2)
1.https://operations.osmfoundation.org/2024/01/25/owg_budget.o... 2. https://osmfoundation.org/wiki/Finances