It's useful to be able to see your saved WiFi networks' passwords. Maybe you've forgotten the password or maybe it some long base64 string that purposely can't be remembered. Being able to see your saved WiFi passwords avoids having to remember to write them down somewhere and still keeps them close to you.

While some Android skins, like Pixel UI and One UI, have methods for sharing saved WiFi networks with other devices, they aren't perfect.

For one, the device you're sharing to has to support scanning a QR code to connect to a WiFi network.
The generated QR code does contain the network password in plaintext, but to get it, you need to scan the QR code with a different device or screenshot it and scan it locally, and then extract the text. And this has to be done per-network.
On Pixel UI 13, the password is directly shown in plaintext under the QR code, but it's still a per-network process.

WiFiList relies on Shizuku to obtain the necessary permissions for viewing WiFi passwords. There's an option to cache known networks so that you can view them when Shizuku isn't currently running.

https://play.google.com/store/apps/details?id=moe.shizuku.privileged.api

WiFiList is open source! https://github.com/zacharee/WiFiList