Bowles-Simpson vs Current Law

Surely the strangest thing about the Bowles-Simpson debt reduction plan is that, relative to current law, it . . . increases the public debt load over the next ten years:

Obviously starting around 2020 or so Bowles-Simpson starts doing better than current law, but it's difficult for the current congress to tie the hands of future congress. After all, the whole point of the "alternative fiscal scenario" baseline is that past law doesn't bind the hands of the current congress. The AFS is preferred my many as more politically realistic than the current law baseline, which is fair enough. But wouldn't it be easier politically to stick with current law than to do Simpson-Bowles' huge series of unpopular changes? After all, the American political system has a ton of veto points. Barack Obama saying "I will veto any laws that increase the deficit relative to current law" would do more to reduce the debt over the next 2 or 6 years than would adopting Simpson-Bowles.