"I've thought about this for a few years. Iruka was simply... he suggested I go through with it to avoid further talk of having the pressure of taking a wife." So that nothing would actually try to split them up.

Of course, the blame wouldn't be on those other parties...they worked under the assumption that Itachi was in no such relationship. So the fault lay on him alone for not revealing as such.

Which is why he had to take care of it, as well as stepping out of a position he never wanted.