I sent an email on the debian-devel mailing list about the way Debian chooses which softphone to distribute:
https://lists.debian.org/debian-devel/2016/01/msg00434.html
For a long time, I feel that distributions have not given this a lot of thought, they just install whatever is part of the desktop environment, even if it is not fully functional. This is one reason people don't have a lot of confidence in free softphones and I feel it also undermines confidence in free software in general.
It would be really helpful if people could give their feedback on this issue in Debian and if you use another Linux distribution, start a similar discussion on their mailing list and send a link to it here.
Regards,
Daniel