All sorts of reason why someone might want to write one of these. There's even a bunch of free tools to help test it (and who doesn't like free tests!).
Until you put fingers to keyboard, you just don't know, it's all book learnin'.
This!
Also writing a HTTP server seems like a hacker rite of passage, like creating your own lightsaber for a Jedi.
So last Christmas, I did just that :)
Personally, I like retrocomputing so I did mine in perl. I learned a lot of things, and I added a few "modern features" as extras like mDNS and cosmopolitan, because it's more fun to use something.local that 127.0.0.1)
It's on https://github.com/csdvrx/PerlPleBean and if you want to dig into mDNS, check the Bonjour part on https://github.com/csdvrx/PerlPleBean/blob/main/experiments/...
It's very fun to be able to launch just one executable and then curl whatever.local