|Because it's inefficient.|
On one of the occasions during which Dan slipped out of his confinement, the baddie he encountered was Brickbat, a death-dealing devil in a spiked cowl and lime-green suit - so he's also a fashion plate! Having enlisted an unscrupulous scientist to develop his signature deadly weapon - a brick which breaks apart upon impact, releasing a deadly gas - the Brickbat's lust for death and greed for smashing people in the face with poison bricks is so great that he promptly murders the creator of his weaponry so no one else will learn its secret (hint: it's a breakaway brick with poison in it).
|"I assumed you had gas!"|
In fact, he's got a lot of them, and he's capable of hurling them in a "machine gun-like" fashion. I guess it's also notable that a single brick is pretty portable, but a whole armload of them is kind of a bear to carry, and you're bound to drop one, at which point you're going to release poison gas ... did Brickbat think this through? Again, one brick, no poison, easy to carry, can be re-used to murder time and time again - across the board, it's superior to the poison breakaway brick.
Anyway, 711 disarms Brickbat by standing in front of a window, through which most of the thrown bricks end up, killing a whole bunch of Skid Row bums I'm sure. With that, 711 returns to his exciting life of incarceration, with Brickbat joining him in a nearby cell ... a cell surrounded by bricks! Ah, irony!