Many things, starting with true support for recent protocols. Until now, no solution were able to leverage multiplexing and couldn't issue concurrent requests using one connection. This permit to avoid useless threading and complexity.
Then, about security, plain DNS is over 30 years old, and we still rely on it to resolve hostnames, it is dangerous to say the least. With support for encrypted DNS and DNSSEC, you raise the bar higher for potential attacker. Then about certificate validation, you cannot be sure the certificate is not revoked without this solution. Almost every dependencies in the chain are SLSA signed, thus almost eliminating some risks.
Finally, getting a fresh evolution without having to re-learn anything or re invent the wheel has some perks. This solution extend the well known Requests and provide both sync and async interfaces, almost no change required.
And more, but I'll let you discover the rest by yourself.
The prefered style of the titles in HN is more dry. The guidelines [1] ask to use the origianl title, but sometimes it's too bad and the subtitle is a good alternative. If you repost it, my sugestion is to use a reduced version of the first sentence "Niquests is a simple, yet elegant, HTTP library. It is a drop-in replacement for Requests that is no longer under feature freeze.", something like "Niquests: A HTTP library for Python that is a drop-in replacement for Requests"