I've been using a local recursive resolver for the past 2-3 years and haven't seen a noticeable difference in resolution times as compared with using my ISP's resolver.

I would guess that using a local recursive resolver (although it caches as well, so that's less of an issue with items in-cache) increases resolution times, but only on the order of tens of milliseconds.

Which is peanuts compared to client/server query response times, especially if requests return data and/or javascript heavy results.

And given that many ISPs mine their customers' DNS queries and sometimes return incorrect (from the perspective of the customer) results, I'd rather not use my ISP's resolvers -- and that hasn't had any noticeable impact on responses to browser requests.

In fact, uMatrix tends to slow things down much more for me as I often have to choose which scripts/3rd party assets/etc. to allow in order to browse a particular site -- or just to abandon the attempt if there's too much cruft.

That especially annoys me when I need to load scripts from several different sites just to view text. In those cases, I usually just close the tab.

Also, they often run a single instance of bind, with little to no load-balancing.

I think these are the main reasons for people to use other dns providers.