Because "if it ain't broke, don't fix it." i'm not one of those users who want to endlessly tweak their ad blocker. i want to set it up, clicking as few checkboxes as necessary to get it going, and then leave it. However, (now) knowing that Cloudflare filters different only each of their servers, i'm incentivized to go tweak a number in the config (as opposed to researching the pros and cons of every possible provider, a detail i truly have no interest in pursuing).
i had no clue which one was active. It was, for me, just a checkbox at the time. This thread prompted me to go check and tweak appropriately.
The upside is there's no single entity receiving all your queries. The downside is there's no encryption (IIRC root servers do not support it), so your ISP sees your queries (but they don't receive them).
Since ISP know your identity, and all it takes is to (request and get) the DNS logs and ISP servitude for all sort of questionable information, you as an identity are giving away all sites domains you visit.
Correction: they can log host names/IPs, not URLs. The path of any given URL is part of the HTTP header, invisible to onlookers (assuming HTTP and assuming HTTPS is uncracked).
So to simplify, the DNS provider has a map of IPs to Domains visited, while the other hand an ISP has a map of IP addresses to identities.
To even cross-reference the data, the ISP and the DNS provider would need to partner, and violate their privacy guarantees.
At the very least it's obvious that using a separate DNS provider than your ISP's provides additional anonimity by decentralizing your traffic. Although this comes with a tradeoff, having 2 providers increases the odds of partial leaks.
This analysis is so overkill for your personal traffic that it borders tinfoil territory, if we are in a professional setting and are discussing the competitive data of a company or that of thousands of users, then this level of scrutiny is merited, but as-is, separating your DNS provider from your ISP is already very marginal and a bit paranoid. Evaluating the DNS providers to such an extent that a huge security company with good legal standing would somehow qualify as unsafe, for the traffic of one user, I stress, is paralyzingly over-engineering the security of an infrastructure that has already been secured such that users don't need to know what a DNS and how to configure it in order to have safe and private internet.
Imagine going to the bank and asking the teller for a withdrawal but not disclosing the amount and coming up with a mechanism to withdraw without anyone from the bank knowing what you withdrew. Sure, it increases your security, but also come on, what are we doing here?
https://developers.cloudflare.com/fundamentals/reference/clo...
if you think a little creatively about how this information could be used by an organization that was created at the insistence of the United States Department of Homeland Security, then you're on the right track.