Updating software is not a panacea and not always the best thing to do. In industrial hardware it's often better to have a known quantity.
Especially with equipment that can cause damage or even kill people.
Even if it isn't quite that high stakes, dealing with constant random updates is a cost factor with no clear commercial gain.
This doesn't mean there can't be updates, but they need to be done on the factory's schedule, not on the schedule of some random supplier.
Also, it's not considered a huge issue in smartphones and laptop computers, but updating firmware on Flash ROM degrades its performance such as data retention periods. Firmware updates are not always a rocket surgery, but like a surgery, not without risks. I think advocating frequent updates to all types of electronics is slightly irresponsible.
Even if a manufacturer publishes updates, the clients would likely not want to change anything, often.
If you have a plant with 1,000 units of gizmo-A and update them during a week-end and now 200 of them do not do the thing they used to do anymore... you have a big problem.
There is a genuine fear to update anything in many industries and I am not sure how this can be overcome.