Well yeah, of course Cyrax's D4 is better than Smoke's, and leaves him with a crap ton of options. Cyrax IS better than Smoke, period. But what do you mean you can't machine gun D4? I don't mean it in the Sub-Zero in the corner kind of way, where you're just spamming 8 frame D4's, even on block. But how many times do we see Wafflez land a D4 on hit, and then go into another one...and another one, and seeing whether you'd duck or not? It's a conditioning tool for later in the game. He's daring you. How many D4's would you take before you duck? And of course, he can always just throw after a D4 on hit.
B23 is not that difficult to hit confirm, and the window to punish Smoke bomb is extremely tight anyway, so unlike 12 net, you wouldn't necessarily get blown up for just throwing it on block (not saying it's a good idea, mind you).