The reason they're not doing it is because they want a piece of the productivity pie.
They're not getting it from me. Ever.
As OP said, it took a lot of effort to get the UI ok. Probably takes even more effort to create a great UI, but I guess Dropbox has some resources, right? Shameless plug: Landing page at https://julesdocs.com
If anyone is interested in pushing this forward, I'd love to hear from you (mail address on the landing page)!
And I will never ever forgive y'all for what you did with mailbox! (Like seriously what did they do?)
Enterprise customers pay more money to have more features with checkboxes in the feature matrix. Telling them they don't get a feature because their needs are too complicated is a tough sell. (something, something, opens up opportunities for low-end disruption, something, something)
Sadly, we never developed it.
But, yes, I totally agree with your rationale. This is the kind of rabbit hole that can quickly turn into a distraction.