Pi-hole has helped improve my "relationship" with Firefox, or better phrased with Firefox forks like LibreWolf and Tor browser. Cool thing with Pi-hole is that you can watch the query log and see what happened in the background while you were surfing the Internet. I learned that :
After removing the sponsored shortcuts in Firefox and putting your own shortcuts there Firefox will make connections each time you start the browser. So, if you would have icons on your quick start page in Firefox for let's say EFF, Lemmy, Mastodon, HackerNews, with each Firefox start up, it would query these sites. which I didn't like so much. Since then I've gone back to a complete blank start page, removing search and all those quick start icons, using just toolbar folders with bookmarks.
Pi-hole defaults to blocking telemetry for Firefox and Thunderbird.
Signal uses Google servers I saw via Pi-hole. I thought that they were using Amazon servers, but looking at Wikipedia for the history of Signal hosting I learned that Signal went back to Google for hosting.
Firefox push notification services are hosted on Google servers. LibreWolf removes a lot of Google things that Firefox has by default, but not the push parts. With Pi-hole it is very easy to block that.
I ran PiHole for years. It started as a way to block ads but then also a way to block games and YouTube for my kids so they get a break. I had to manually control this though. I switched to NextDNS last year because this can be done on a schedule and they can't get around it such as swapping to mobile data on their phones.
In the house though I run AdGuard because there's no way differentiate traffic for each of my kids NextDNS profiles. With AdGuard it can proxy DNS requests to take traffic from the TV in their bedroom and convert it to DNS over TLS so the traffic hits the correct profile. I don't use AdGuard for anything else. It does not filter anything. It's purely to make sure traffic hits the correct NextDNS profile.
Why maintain the same thing in multiple places? If the pi-hole is blocking it, the pi-hole is blocking it. What added value is there in also maintaining the hosts file?
The amount of times I've seen people request help because Pi-hole was not blocking/functioning properly, well a hosts file just ensures nothing leaves that you want blocked. Besides, you may have different machines set up to be strict or permissive depending on their use case.
DNS services with blocks lists such as Pi-Hole, AdGuard, NextDNS, etc, provide a centralized config file for all devices on a network, so you only configure once, collect statistics, have built in block lists that can be easily modified and updated either automatically or manually and are fast.
Using large lists in a host file will slow local resolution. It wasn't designed for this use case as it's acting a flat file database with a limited amount of RAM allocated for the process and will get slower the longer the list. While this latency won't be noticeable in the thousands of lines, once you start hitting hundreds of thousand or millions of entries it will start to crawl.
Hosts file are also unable to RegEx or Wildcard entries which means you would have to duplicated lots of variations in domains...
I mean I can also statically assign IPs to ever client and keep a spreadsheet, but why don't I just use DHCP?
Absolutely. These lists are created by server admins who collect what the firewall rejects, much like you see with the Pi-hole. They'll automatically block some ads and many threats too. Another tip if you're using Librewolf, Mullvad browser or Firefox with uBlock, enable more of the filter lists.