Okay Andrew lets say you renovate your existing house, though it may look beautiful on the outside, and has all the flare of the million dollar homes.
The only entrance is through a doggie door, because the hinges were the wrong size, and instead of getting the correct hinges, you nailed the door shut to the frame, and cut in a doggie door.
Ok great we are in now.
Whoa what the heck, the floors were started but they ran out of material in the center of the foyer, so now you have to beam walk, see more careful not to fall in between the joists.
Oh wow look at the size of that bathroom, man that is a nice tub, but you reach for the knob to test the shower pressure, the knob falls off in your hand! Dang, so you report that to the builder.
The toilet is nice looking, updated version, you raise the lid and it falls off in your hand! hmmm.
You then go to flush the toilet just for testing purposes and the water has back pressure from faulty plumbing, the water spews in your face, well damn!

Ok a few minor glitches, that need some enhancements....Need i continue...