So I’ve recently learned how to use a mill and I thought, what’s the point of a mill if you have a CNC router or something. Not just in FRC but in industry and stuff, what purpose does a mill serve over a router
CNC machines require programming (CAM). Often times it’s quicker, cheaper, and easier to skip the programming step all together, whether because the operation is simple, the part is a 1-off, or any number of reasons.
I think you’re confusing a couple of different things here. Routers can be manual or CNC. Mills can also be manual or CNC. (As can most other machine tools-- plasma cutters, lathes, brakes, etc.) For the most part, the type of operation and material governs what sort of machine you use. If you’re in a production environment and want to make parts faster, you can buy a CNC version of that machine.
In the FRC world, a CNC router is most often used to cut pieces from sheet aluminum or polycarb. Some people also use them to cut holes in square or rectangular tubes.
A mill tends to be used on smaller workpieces including ones much thicker than what a CNC router can accommodate. A mill is not suited to working on sheet stock.
Generally speaking mills are usually quite a bit more rigid than routers. This is useful when there are higher cutting forces. For example when you are cutting harder materials or taking aggressive cuts with larger tools.