Squirrel is abandoned for years and still used anyway, often by people who don't realize it's abandoned. It's the default if you use the Electron toolchain, so that's why. It has serious design problems too, like it breaks Windows networks by bloating people's roaming home directories with dozens of independent copies of Chrome which then get backed up, copied around on login etc. Admins loathe it as the whole point of this design is to bypass their ability to manage their own deployments, although they still get the blame when things break, of course.
There's a better way, which I am shamelessly self-promoting in this thread (as it's 100% on topic) - my company makes a tool that can ship self-updating Electron apps and beyond being not abandoned, it's got a lot of really useful features, like being able to do the build and upload of signed updating packages (using the tech MS is pushing here) from Linux CI workers, without needing a Windows license.
It can also do forced updates on launch, which can be helpful for apps where the protocol between client and server changes regularly. And it plays well with corporate Windows deployments. People can install apps locally without needing administrator access but it goes into c:\Program Files