It comes pre-installed on many machines, and the mindshare is large.

I also attempted to remove Norton from a friend's computer a few years ago. I failed and later discovered that was actually unable to be uninstalled. Norton published some instructions to let you remove parts to the point you could ignore it at least.

I swore to never to touch anything from Norton/Symantec ever again. I bought ESET/nod for a few machines but now I rely entirely on Windows Defender for the few Windows machines I own.