I have the soldering iron that is based off, the TS100, and it's really useful. The CPU lets you regulate temperature, and it has features like lowering the temperature when you don't move it for a bit. That's what the CPU is there for, it's really just a microcontroller. Good luck making a (minimally decent) soldering iron without one for temperature control.
I think this is likely to be down to the different expectation/requirements of people who use their soldering iron a few times in 30 years, compared to people who have theirs hot most or every day.
I bet your soldering iron is fine for everything you want it to do. I also be it won't let you work with tiny SMD components or reattach micro usb connectors out at the drone field where you damaged it in a crash...
There are some cheap DC-powered soldering irons in a similar form factor which use a dial and potentiometer to set the temperature and an op-amp for temperature regulation. No processor in sight. Apparently they work reasonably well.
Does it give you a digital display of the temperature (in Celsius or Fahrenheit, configurable)? Does it sleep if not moved? Can it run off a battery pack and monitor the power of said battery pack to safely shut off?
Not everyone needs those features. If you do or want them, the moment you add even the simplest logic, you are better off getting a microcontroller already. No reason to bother with discrete logic chips anymore.
I have used for many years a standard soldering iron (not even a soldering station) with zero logic whatsoever. It worked, but nowadays I prefer to be able to set the exact temperature I want, to the degree. And to be able to monitor if the iron is able to handle the thermal mass I'm trying to solder.
