Query statistics is valuable data you can sell. Client DNS queries are in that regard similar to search queries and a default search engine setting, you can sel

Query statistics is valuable data you can sell. Client DNS queries are in that regard similar to search queries and a default search engine setting, you can sell that to the highest bidder. So browser makers are incentivized to implement their own resolver with its own set of DNS servers instead of just the system ones. Either because they want to sell those statistics themselves. Or because they want to protect their users from the statistics collection of the underlying OS resolver or ISP resolver.