I've heard that Zeiss's quality is very good/great but I'm also curious if it has anything to do with the "manual focus only".
I have read this question but it only partly addresses my question. Is it a company policy or what?
It is one of the lens design compromises they have chosen to make. While I don't think anyone can know for sure the reasons behind that decision, I can think of several likely ones:
It probably has as much to do with the fact that they're an OEM lens maker for Sony as anything else. Yes, Zeiss does make autofocus lenses for DSLRs, but they're co-branded for the Sony (Minolta/Konica Minolta) system (which is why I cringe every time somebody says there are no "professional" lenses in the Sony lineup).
All of the following are made in Sony α (Minolta A) mounts:
(The 16-80mm lens is designated "DT" and is for APS-C sensors.)
You may see OEM manufacturers making gear for other systems occasionally (notably Tokina, whose agreement with Pentax allows their co-creations to be marketed for other mounts), but there's a pretty good chance that the agreement between Sony and Zeiss doesn't allow them to sell autofocus lenses for competing mounts.