I’m not sure what they expected, not everyone runs and gets a new ARC just because of that immediately.
By chance I got a new ARC about a month ago and I got one which supports the mobile ID, but when I started looking into it how to set it up I couldn’t find a straight forward description, especially not in English. This is why I still don’t have it even though I was low key excited about that possibility.
I changed my visa in January, so I ended up with the new card, and I installed the app and set it up. It was relatively easy… by Korean app standards. However, at the immigration office, they had signs up saying that the old cards were still valid until their expiration dates, so there was no reason to get a new card if you were only there for a standard visa renewal. The new cards also cost 35,000 won instead of 30,000 for the old cards, so of course people aren’t going to be rushing to the least pleasant place in the country just to wait in line and pay extra for a new card they don’t need!