As a retired software engineer, I can say it’s likely because the hole is really deep. No engineering company has the resources to tackle every bug report. I was working on a ten-person team for a Fortune 100 company everyone has heard of where there were at least 2,000 bugs outstanding at all times where half would never get fixed due to lack of priority or severity. That’s just the way of things. With an OS there are likely hundreds of thousands of bug reports, many of which may not see the light of day for years, if ever.
One bug report I submitted to Apple was three years ago where I reported the OS didn’t work right with my monitor whereas the prior version worked quite well. Many monitor resolutions were missing that existed before. It took more than two years and two major macOS versions for me to get a reply to it that it was finally fixed. I didn’t care at that point since I had moved onto a different monitor I liked better. I’ve submitted quite a few bugs and that was the only response I ever got to any of them. It’s also possible there are many duplicate bugs and they just close out those duplicates and never get back to the person who submitted them.
They see your bug reports. It may just take them until iOS 21 to get to them.