Since when was it faulty?
Since it was originally thought of?
It bypasses all of that effort that was put into optimizing Blockland for the large brick loads we enjoy today. When used sparingly, they don't cause a tremendous performance hit. But the fact of the matter is that we shouldn't be required to use certain bricks sparingly. We have a system for much more efficient bricks and it should be used.
Furthermore, there's all kinds of bugs that get introduced when you don't do it the right way.
- Being able to build on parts of the block that don't have supports
- Stud textures rotating with the model
- Collision issues
Some of these issues can be resolved by modifying the BLB file,
but this system actively encourages you to not learn how to write propper BLB files. There's plenty of documentation now, enough that you should be able to make your own bricks if you experiment a bit.
The only exception is of course animated bricks, which Space Guy already noted.