Available parts have been a big problem since 2012. Parts are prioritized to production line first. That has caused delays for body shops and general repairs.
If parts are plentiful as I assume with air bags, it still took quite a long time for my case.
I got a 2012 Model air bag recall since January 2017. Service Center said they'll get mobile service in Fall 2017. It finally was done when I brought my car in for annual service in Summer 2018.
That's for 2,650 cars that were delivered in North America in 2012.
That's a small number comparing with the numbers of cars with HW 2.0 and 2.5!
2017 production was 120,000
2018 production was 350,000
For 2 years alone, that's
470,000! (HW2.0 didn't start until 10/2016, so it's only about 2 month production at most)