They are great cheap training tools. We use them for basic punching drills like described here and held out at arm's length just for the conditioning.
We also use them like meihua posts, balancing on them while doing stance conditioning or centering exercises.
Sitting on my butt and posting here on the forum is convenient. I'm not always looking for convenience when I train. I'm looking for challenge. There's something crude about working with bricks that I like. Reminds me of training in China.
Well, sure, but I don't work in either place. I sit on my butt and post here on the forum. So I need to lift weights sometimes. Or at least, lift some bricks.