Incoming links: Microcontroller
Many/most microcontroller boards have analog-to-digital converters built into them, it is very convenient. E.g. it is the case for the Raspberry Pi Pico.
It basically replaces a bunch of discrete digital components with a single chip. So you don't have to wire things manually.
Particularly fundamental if you would be putting those chips up a thousand cell towers for signal processing, and ever felt the need to reprogram them! Resoldering would be fun, would it? So you just do a over the wire update of everything.
Vs a microcontroller: same reason why you would want to use discrete components: speed. Especially when you want to do a bunch of things in parallel fast.
One limitation is that it only handles digital electronics: electronics.stackexchange.com/questions/25525/are-there-any-analog-fpgas There are some analog analogs, but they are much more restricted due to signal loss, which is exactly what digital electronics is very good at mitigating.
First FPGA experiences with a Digilent Cora Z7 Xilinx Zynq by Marco Reps (2018)
Source. Good video, actually gives some rationale of a use case that a microcontroller wouldn't handle because it is not fast enough.The History of the FPGA by Asianometry (2022)
Source. A Microsoft format for flashing microcontrollers by copying files to a magic filesystem mounted on host, e.g. as done on the Micro Bit and Raspberry Pi Pico.