Again, I'm not talking about machinery that actually needs PLCs, I get that. A lot of stuff doesn't have vibrations, temperature, safety issues etc. but is built around PLCs out of tradition and BoM reasons.
"Here's our end of the production line fan that blows dust off of your product for $4k because we used a PLC." There is lots of stuff like that that just has no business using a PLC.
I (thank god) got out of manufacturing IT around 2000 but I still have friends working in that industry. A guy I know makes an absolute fortune frankensteining old MFM drives together and fixing resistors on 10base-T network cards because someone thought the exact same thing and subbed out a PLC for a computer to save a few bucks.
Trust me, I loathe PLCs, but Allen Bradley will still sell you a drop in replacement for something the now retired previous guy put in service 15 years ago.
Yeah I'm out of it now too. You still have the same issues running PLCs. I've had to find old ass network cards on EBAY. I understand why PLCs are used. I turned down a project building a machine using Arduino's and raspberry Pi's because it was inappropriate for the application. But there is definitely a subset of manufacturing equipment that doesn't require PLCs. I've already seen it happening scanning networks and seeing devices show up with RPi MACs.
"Here's our end of the production line fan that blows dust off of your product for $4k because we used a PLC." There is lots of stuff like that that just has no business using a PLC.