As hinted with the Finder comment, "Spotlight" is behind much more than the command-space search box. I don't know what the Siri services might do other than Siri itself, but wouldn't shock me if they were involved in things like Shortcuts and Control Center widgets. I understand thinking things you don't use are simply a "waste of CPU and storage space", but this reads like the kind of posts I used to see in the Windows XP era where people would open Task Manager and kill random processes they didn't understand. Best to make a little more effort to understand what the OS is doing before taking a scalpel to it. Or if you'd rather not, there's always OpenBSD (being serious here, it's pretty cool).