[crote]

Analog control circuitry is also really hard to patch in production, or to adjust to different behavior during design.

Oh, you need a quadratic fan curve instead of a linear one? Have fun starting from scratch!

[wildzzz]

You can definitely make a PID controller just with opamps and potentiometers.

[crote]

I bet you can. But you can't turn a simple single linear amplifier into a PID controller with zero physical changes, can you?

My point was that, if you want additional behavior, you need to bake that in from the start. With an MCU you can trivially switch it in-the-field to literally anything you can imagine.