Why y'all going to your fav search engine first to search with another search engine? This is built into chrome and probably Firefox and every other browser
Bangs make searching third-party sites easier. For HN, for example:
!hn by:dredmorbius ddg bangs
(I don't know how to force that to search comments by default, but that's a toggle on the results page.)
Others are image, weather, and Wikipedia searches.
You can share your bang searches with others. Since the syntax is centralised, you're not working through other people's individual search shortcuts.
DDG maintain the bangs and generally update the ones that break. Since more people are effectively testing these all the time, this is more effective than your own ability to keep your own search shortcuts in working order.
My claim isn't that these are necessarily overwhelming advantages. But they are benefits which some of us have noted and appreciate, and show that the concept has more than nil value.
And: DDG have over 13,500 bangs and counting, and you can search for relevant bangs using, of course, the !bang bang search, e.g.,
My usual use case is to search HN comments. Problem is that there doesn't seem to be a way to specify comments on the bang search itself, so you have to toggle the results page option, or click "search for comments" to get the 57 (at this writing) comment hits:
I really wish the bang would default to comment search, as it's a much broader search target. Posts are limited to 80 characters, comments to rather more than that (there is a max comment length, and I've hit it, but it's fairly generous). So your odds of matching term(s) in a comment are higher than for posts.
I don't know how the syncing works for that, but all my custom bangs (which for me includes bangs for Kagi lenses / filters and non search engine sites at this point) sync using my Kagi account which is pretty nice.
Also I use Firefox Focus on mobile, which doesn't have many settings, and I don't think I've seen that features there.