It's sad that it took legislation to make this happen, but I can see why. I worked in a pseudo-Apple-store during the height of the 30-pin dock connector and I sold so many cases, speaker docks, charging cables, and all sorts of weird accessories that were built for the 30-pin connector. Then Apple switched to Lightning. It was better in every. single. way. And yet people got burnt. There was so much hardware that wa…
1. As you mentioned, most accessories have moved to wireless. I still (usually) use a physical cable for charging, and I guess I have a 3.5mm dongle, but I think those are the only two things I've plugged into my iPhone in years. Docks with a physical port, in particular, were super popular 10+ years ago and don't really exist anymore. People won't be throwing away speakers.
2. They aren't switching to a new proprietary port, they're switching to a standard port. Which means there's already a thriving ecosystem of accessories that will now be usable with iPhones (some of which people may already have, for use with their other devices!)
I'm more cynical in my interpretation of Apple's motives: I think they just wanted those licensing dollars