Why should the workers settle for only higher taxes and slightly more social programs, the workers deserve everything because without the workers there is nothing (furthermore without the capitalists there is everything).
Because we do not fight under conditions of our choosing, we fight where we stand.
Taxing the rich is a short-term solution, but it's one that we can do RIGHT NOW that would be a step in the right direction. You can't just quit capitalism cold-turkey without a bloody revolution. You have to take steps to transform society in a gradual manner.