Google/Cloudflare tackled the UX of free DNS spectacularly with these gold IP addresses. It's the primary reason I use them instead of OpenDNS, which was an earlier player in this space.
Between that and some of the content filtering options you can get with the paid plan, I find that it's a very full-featured option for homes with young kids. I'm pretty sure you get to control the logs on the paid plan too. Need to double check.
Presented as a weird, intermittent, "hey the internet is out" at the office around the same time each afternoon.
We talked to the APNIC team about how we wanted to create a privacy-first, extremely fast DNS system. They thought it was a laudable goal. We offered Cloudflare's network to receive and study the garbage traffic in exchange for being able to offer a DNS resolver on the memorable IPs. And, with that, 1.1.1.1 was born."
There is a lot of documentation, Cisco being one of the primary at-fault companies, that uses 1.1.1.1 for all kinds of various internal configuration.
Given hundreds of thousands of devices configured with 1.1.1.1, even a simple misconfiguration on just 10% of those is a lot of garbage traffic.
What cloudflare don't say in any of their materials that I've seen is the agreement is for an initial 5 years, so YMMV after that.