Silber,
Apologies for causing the angst and I'll desist immediately.
"Unrestricted climb" appears perfectly sensible but it can have upstream implications, so its use causes controller angst. Accordingly, we have instructions not to use "unrestricted climb" but to rather use the correct ICAO procedure. The ICAO requires that each SID restriction must be specifically cancelled (although in reality this problem is RNAV coding and not SID restrictions). There's nothing wrong with the ICAO but its very cumbersome if the airspace is not well integrated. For expedience, some Departure controllers do use "unrestricted climb" but this causes the majority of non-local operators to, correctly, challenge with, "Confirm the XX **** foot restriction is cancelled?" All this challenging creates a lot of RTF traffic.
Anyway, some of this should all be cleaned up in a few weeks time.
Of interest, I understand, ICAO intended to introduce "open climb/descent" in January 2013 but this was questioned by the FAA who were using "Descend via STAR" and introducing "Climb via SID". Here is video of how the FAA explains their change:
https://www.youtube.com/watch?v=LrPzv96VBp8