1. Rust is gaining much acclaim for writing safer code, a good package management system, a very friendly community and other things. So it's natural that people would be interested in knowing more about libraries, frameworks and tools that would allow them to use Rust for whatever they're working on now or plan to work on soon. Not many people would want to develop their own HTTP handlers or image decoders or message queues or anything else just so they could write their primary project in Rust and gain the advantages it provides. Libraries are a huge part of that bridge that people need to use a language more (one big reason why Python is preferred across different subjects is because of the libraries).
2. This could inspire someone to go to these or other repositories and contribute to them.
3. Considering that images (and JavaScript) make the bulk of web pages nowadays, I'm sure many people would want to know about pure-rust libraries that handle images so that they could now have their web backend projects use more of Rust with better guarantees on a few aspects (like stability of execution, for one). Outside of web, this could also appeal to people who write imaging related applications.