Bear with me while I think aloud:
When you push on the brake pedal, it activates a "piston" or some such (Don't know much about the details of the design of the master cylinder). This "pushes" on the brake fluid that fills the lines down to the tires. These lines should be filled hydrostatically (ie no air bubbles, liquid all the way). Normally, there isn't anywhere for the liquid to go, and, becuase liquids are "noncompressible", pressure is generated. This pressure "actuates" the brake pads/shoes.
The lines are bled, so there should be no air in the lines to interfere. But something works right, because you can pump brake fluid out the bleeder ports. The fluid has to be going somewhere, or the "piston" in the master cylinder won't hold the pressure.
I see two possible reasons not to be getting pressure built up: a leak, or something wrong with the brakes at the wheels.
If it were a leak, I would think it to be a large leak, considering there is no pressure being generated. Also, if it were a leak, you should see the fluid level drop. I'd go over the system very carefully, and make sure there isn't a leak.
At the wheel, if the brake pads/shoes aren't contacting the rotor/drum when you press on the pedal, they will move until the pedal hits the floor and stops moving the brake fluid. Disc brakes are self adjusting in that they don't retract back the the original position; they have no springs. So if the front brakes are not adjusted, a few pump on the pedal and they should adjust themselves.
The drum brakes are also designed to be self-adjusting, but the mechanism is a bit more complicated. If the adjusting mechanism doesn't work here, then the retracting springs will bring the shoes back to the original position. This could mean the shoes are never contacting the brake drum, and therefore no pressure is generated when you apply the brakes. Or, if the wheel cylinders are not contacting the brake shoes, then they are "pushing" against dead air, and no pressure will be generated. I'd pull the rear brake drums and make certain they are assembled correctly. I'd also check the adjusting cable/pawl/screw to make sure they are functioning. You can check the current adjustment accessing the adjusting screw from the back side of the wheel assembly. Using a screwdriver you can turn the screw until the shoes are against the drum. Which makes me remember that the adjusting mechanism (particularly the screw) is side specific. If you had the left adjusting screw in the right wheel, It would retract the shoes instead of expanding them. That may be something to check, too.
That should give you a good start. I apologize if I've been long winded. For me, it helps me solve my problems if I can think through the normal operation of the system and identify where problems could be.
