Standalone controllers are often used by 3Dprinters. Hobby milling machines are often controlled by a program running on a PC, laptop, tablet, Raspberry, etc.
My 3D printer has a standalone controller but the lathes, router and rotary table require a windows computer. For my router (milling machine) I use UGS to send the gCode to the (grbl) controller. That works OK especially if I want to pause or stop the running program to change the settings (feed, speed, cooling, cutting depth, etc).
Because my space is limited, I use a tablet for the lathes and rotary table. The router currently is connected to a laptop but I am considering a tablet to free up space.
I use WiFi to connect so any machine can be controlled by any PC/Tablet/Laptop.