RFC 1035 did in one part suggest a model in which some bigger more powerful machines may run a recursive resolver as the local resolver, but other machines woul

RFC 1035 did in one part suggest a model in which some bigger more powerful machines may run a recursive resolver as the local resolver, but other machines would probably use a stub resolver that redirected a local service running a recursive resolver as a service to the network. This had benefits like the centralized cache of the local networks' recursive resolver being more beneficial. Implementation wise, most implementations are either stub resolvers, or full blown dns servers capable of serving up arbitrary sets of domains authoritatively. There are fewer implementations that do recursive lookup without a full authoritative server implementation. Obviously including a full capability DNS server in every OS install is absurd, so they come with with the stub resolvers instead. And originally when the Internet was just big organizations connecting their networks, each network running a recursive resolver for the other machines made sense and worked fine. But along comes home internet, where originally just one machine running windows was getting connected. ISPs could perhaps have required users to run their own recursive resolver, this would be painful, and inefficient. (Keep in mind that a recursive resolver's cache is more efficient the more machines it is providing services to). So the ISPs ended up running recursive resolvers for customers. But now since the ISPs customers don't all trust each other, concerns like cache poisoning become possible, which were not much of an issue when you ran and trusted your own networks recursive resolver.