Why do industrial panels for oil and natural gas compressors or other industrial equipment use terminal blocks for wire management? I have been doing some repairs for companies and was wondering why they chose that layout. I was thinking instead of all these wires going to different terminal blocks why not make a industrial PCB? Is this possible? Is it considered bad practice?
Why of course, making industrial PCB is possible.
But also, there are good practical reasons for using wires and terminal blocks.
Control panels can be large
A typical limit on PCB size is about 0.5x0.5m. The limit is set by the size of a PCB laminating press. Control panels can be much larger than that.
Dealing with high currents (above 10A) on the PCB is possible, but it requires wide traces. A medium sized 18AWG wire is rated for 15A. High currents encourage to use wires.
Relatively low quantities
Makers of industrial control panels like to use ready-made blocks (thermostats, displays, alarms). They come in standard sizes: 1/8, 1/16, 1/32, DIN rail. They have screw terminals as a way of interfacing to the rest of the system, so you have to have wires to interface to them.
Long service life requires maintenance in place. Ideally, maintenance should be possible without specialized tools. Screw terminals need only a screwdriver.
Vibration is killer on connectors. Screw terminal blocks are more resistant to it than pin connectors or card edge connectors. Connectors are one of the most common causes of failure in electrical systems - reduce the risk of their failure with more secure connectors like screw terminal blocks or mil-spec connectors and you stop seeing as many failures.
Also loose connections that are about to break are serious danger in causing fires. The question mentioned oil and gas industry. One spark in wrong place there can be critical and cause loss of many lives. IEC Standards also stand for usage of proper installations and because of these standards there are several blocks created to make these secure installations easily.