Vermin control on farms is MUCH easier with a semi-automatic than with a bolt action rifle (seriously), our family no longer has a farm so it doesn't effect me personally but that doesn't change the facts for a large number of disadvantaged farmers with vermin issues.
And there are a number of international sporting events that require semi-automatic guns to compete in, sporting shooters wishing to compete in those events cannot normally purchase the guns to do so which has wiped out whole sections of the target shooting market hurting sales and jobs.
That's just two reasons.
On top of these there is the whole 'divide and conquer' problem, by politically isolating hunters from fishers and from 4 wheel drivers and dirt bike riders (and from each other) and splitting the 'outdoor lobby' into smaller groups the government (and more worryingly the Greens) can 'manage' us easier, that's not a good outcome in the long run for any of us.