> Or printing the bricks like Lego so you can just collect them together.

Are construction bricks not already essentially 3d printed? They're 3d objects produced on mass to aid in affordable and standardised construction.

We've been "3d printing" stuff for years just with different methods like injection molding. The 3d printing your referring to in contrast is generally more expensive per unit and the only real advantage of it is its flexibility which is why it's used often in prototyping, but wouldn't be of much use in the mass producing of affordable homes (or anything for that matter).