It's of course about lock-in. In the early Web-GIS era there were a few competing but popular notation standards for sharing lat/lon/zoom/<sometimes more> that was meant to be human readable and compatible with any WMS or similar.
Ah... to imagine a world where you could just share a coordinate string and people could open it in whatever map app/page they wanted. Geo URI is probably the closest we have today but I don't think much of anything outside the OS Geo community accepts it.
I think that's actually a separate issue. What I specifically want from a Google Maps share URL is for it to be something I can send over text that will reproduce for my recipient exactly what I see.
A lat/lon/zoom/start?/dest? is kind of what a Google Maps share currently is, but it's neither an interoperable standard nor a reliable capture of the current state, so really the worst of both worlds.
(Also, hi AB! Nice to see you on here)