in absolution he was no longer employed by the ICA, so he does not wear his professional work clothes anymore. 47 actually had a reason not to wear his black suit and red tie.
for example in hope, 47 was wearing his black suit, but without the tie or gloves. this suit was ok, because he was no longer employed by the ICA and does not wear his professional clothes, and his suit in hope was not extremely different from his iconic suit anyway, as he is still wearing a black suit and it fits with 47's taste in clothing. his suit in hope was more like his casual clothing than his professional clothing.
basically what i'm trying to say is that in absolution, 47 had a good reason not to wear his iconic suit. in HITMAN, with the exception of hokkaido, he does not.