Think of the cost!
I'm now involved in the upgrade of radio bits in public transport vehicles for passenger announcements, which is nowhere near critical, just convinence for public. New hardware (or add on as in our case, so just the radio bit is updated) is a fraction of the cost. Real cost is labour, and these bloody things got wheels and mind of its own so catching these to do the work is a challenge! I can't imagine headache to do it times millions of affected devices. It's years of project planning and a lot of £¥€$