probably because nobody has coded it yet.
But what if the platform owner refuses to merge the feature? For traditional local software, it is never a issue.
the problem here is that a remote service is a black box for the user, whether its source is Free Software or proprietary. But that's a whole other issue.
I do not think it is "a whole other issue".
Free Software does not mention software's functionality. Because it assumes a software's functionality can be extended given the freedom to access the source. But this assumption is not valid on remote services.
That's why I think "proprietary platform" is a vague term.
Not considering self host, I personally cares 1 more than 2:
- platform providing open data
- platform using free software
Sure, 2 provides the freedom to self host. But sometimes self host is not possible. For example, if identi.ca is closed, I may self host pump.io (or other alternatives). But if google search engine is closed ( and releases all source code under a FLOSS license), I cannot self host google search.