I think, after iterating their sync technology over and over, they consider it as a "solved" problem. Besides their macOS (kernel modules related) Smart Sync woes, there are not many problems they're facing now. They intentionally keep the Linux client as barebones as possible, but I'd rather not die on that hill today (it's late).
So, they're trying to build an ecosystem around their user's files, so they can both capture more files (growth), and create value from this file trove.
I understand their position, but they're also hurting their own user base who want basic file syncing by ignoring them (e.g. people who want a better Linux client, KDE compatibility, macOS M1 smart sync woes, etc.).
If they solely focus on file sync, there are other competitors coming fast, too (Google is cheap, iCloud is cheap, pCloud is European, etc.), but keeping the integration, performance and features moat is the only sensible strategy for them, at the moment.
I don’t think they have a given distribution at the target audience they need for this. The examples you gave were just a simple upsell or a package deal to their existing audience.
A huge chunk of these digital products sold on the internet today link to Dropbox. So the value add is really them removing an extra step in the process for the creator.
