People don't appreciate what is free
I've found over time that when something is free people don't really appreciate it. Even worse, they can become very demanding and even downright nasty when free stuff isn't done perfectly and to their expectations. Early on the Habitat for Humanity folks had a problem where the houses they gave to the poor were being stripped of anything of value (including the wiring in the walls) and abandoned. They instituted a policy where the families receiving houses had to work at least 20 hours a week on the homes they received. Even if this meant bringing volunteers water during breaks. Lo and behold, the problem went away as the families understand the amount of work and effort it actually took to build the house they received. My problem with the bottom 50% not paying taxes is they don't feel any of the pain associated with the benefits they receive and therefore all they want is more! If every time some new program or benefit increase occurred there was at least some token tax on wages for the bottom 50% I believe people would pay better attention to what they consider to be really important. This is human nature, something that both parties seem to ignore or exploit quite often.