It is surely not the default frontend on many business that still rely on native apps, on mobile devices, device displays, air gaped networks, factory automation and robot control systems, ....
Yes, but the web browser is ubiquitous so it's naturally going to sponge up defaults.
If someone's mad that people don't auto-assume they design robot neural interfaces when they call their self a front-end designer, then they're just fighting their own ego.
Technically command line programs are also front end.