I think the same question can be asked for why lots of equipment seemingly requires an OS. My take is that these products went through a phase of trying to differentiate themselves from competitors and so added convenience features that were easier to implement with a general purpose computer and some VB script rather than focusing on the simplest most reliable way to implement their required state machines. It's essentially convenience to the implementors at the expense of reliability of the end result.
My life went sideways when organizations I worked for all started to make products solely for selling and not for using those. If the product was useful for something, that was the side effect of being sellable. Not the goal.
Worse is Better has eaten the world. The philosophy of building things properly with careful, bespoke, minimalist designs has been totally destroyed by a race to the bottom. Grab it off the shelf, duct tape together a barely-working MVP, and ship it.
