Because job creation is a lot more complicated than just reducing taxes, it is not as simple as a lot of fiscal Conservatives want to make it appear. Other big factors depressing job creation are oppressive and omnipresent regulation, litigation risk (From labor cases to product liability to class action suits to the NLRB not liking your new factory location to...well, 'nuff said), the difficulty of borrowing money, and just plain uncertainty. Lowering taxes alone does not necessarily create jobs.
However, since none of those anti-job factors are going to change (At least not for the positive) under the Oministration, one thing is crystal clear: RAISING taxes will KILL jobs.