In this example, except for an administrator spying on other users on a shared machine, which is kind of already an admitted risk by users on a shared machine anyway.
...as a Linux systems engineer, you are many times faced with debugging a black box problem wrapped in SSL on both ends which you need to peek into to understand what's going wrong; there is nothing suspect about this technique in this environment, it's what you're paid to do (solve problems). It's basically like having the ability to elevate your NIC port to promiscuous mode to debug an issue (tcpdump, e.g.) - it's a tool with no opinion, the human operating it is the one to be worried about.
It may be also helpful when reverse engineering "proprietary" protocols, e.g. to create compatible clients.
It may be even easier to just "mitm" the traffic like this in applications you develop yourself to find out what going on deeply buried in some third party library. Easier than modifying the code or attaching a normal debugger.
There are plenty of legitimate uses.
There's just so many things you can so. The original goal of the post was to tamper with zoom's attention tracking for example (which was a field in one of their protobuf payloads).
It's very much an operational kind of thing if you are trying to troubleshoot a thorny issue with your app in production.