I released the Rust library that downloads and reassembles media segments from a DASH stream (https://github.com/emarsden/dash-mpd-rs). Won't release the web scraping bits because they are against website terms and conditions, and because annoying countermeasures will be implemented if too many people use them.
You can run a local bundle of HTML/JS/WASM in a web browser instance that you isolate (for example with firejail) to prevent network access. You distribute as a zip/tgz, but it's not obvious how to handle updates without a full redownload. Distributing with a full Electron-like interface is obviously overkill.
If you're running a web app that's hosted elsewhere (which will be much more convenient for most people), your web browser or the software isolation functionality (or firewall/proxy) needs to distinguish between the initial resource loads (approve) and later sneaky logging requests (ban).
There are Android applications such as TrackerControl that have related functionality (operates as a local VPN to filter all network requests and block tracking) but I don't know of convenient tools for the desktop (Linux, in particular).
Open source runs in a large amount of trust, and we're all complicit.
This is a concrete problem when deploying apps that need the user to “upload” some sensitive content.
A second reason is simply costs to the public. In 2019, the interim FAA director Dan Elwell testified to the US Senate after the 737 Max disasters that bringing all delegated oversight back into the FAA would require 10000 extra staff and USD 1.8B in costs. There are fairness/democratic arguments to having the costs borne by the industry (and thus indirectly by the privileged portion of the taxpayers who consume air traffic) rather than by all taxpayers.