. . . mainly because republicans don't give a wit about any of the incentives or concessions the President included.
Like you say, ProSense, there are many good elements to this budget. there are also many politically unrealistic things in there, so, we have to consider it, I think, as more of a political statement. As your title suggests, they want to put the focus on republican insistence on protecting their wealthy tax loopholes and their willingness in their budgets to have middle and working class taxpayers pick up the tab.
Also, by spelling out a 'cut' in 'entitlements, the President hopes he has put the spotlight on the republican stage where he expects they will finally be forced to spell out their own idea of cuts and make clear what they will defend and protect; mainly their own taxpayer-derived wealth.
Problem is, republicans have shown zero sincerity in this debate. They responded once to a firm stance by the WH during the last fiscal showdown. No weakness or daylight to support and their posturing lost oxygen. The President's proposal gave them some oxygen. Maybe not enough to overcome their own vacuous concern for SS and Medicare - outside of the type of reflexive bashing like the RNC did today over the President's SS proposal -but enough to sustain their delusions until, perhaps, the next election.
That's what I think this budget document represents, and I think the challenge to own the definition of it will consume the pending campaigns over the next several months. I think the WH has a long and hard slog to turn this into a debate over 'inequality;' much like the hard slog during the last election.