Going from 8.9% to 8.5% is a 5% reduction in flu cases. If this translates to 5% fewer sick days during the flu-period and a 5% reduction in doctor visits that are due to flu symptoms (some people go to the doctor for everything), that can absolutely be a reason for the government to want people to get their flu shots.

Personally I have never had a flu shot and am not inclined to start doing so, but I know people who have and according to them, if they do get the flu it affects them less in the years they get their shots vs. when they don't. So assuming that the flu vaccine is harmless and the cost is not too great, it can make sense to get it even if the effectiveness rate is low.