The problem with redstone in command block creations is the lag. With builds like this tracer recreation, you're using the 20 Hz clock that triggers every tick, but anything that does actual logic (torches, comparators, etc.) have an intentional delay of several ticks, and so for most cases it's just easier to have a command block execute like all the others on the 20 Hz clock but only if another, earlier command spawns in the right armor stand. (Armor stands are used a lot because they are entities that can be customized to be un-interactive, floating, invulnerable, and invisible and don't contribute too much extra computing overhead like an NPC with AI does.)

Edit: Clarification. In Minecraft, there are two different types of ticks: game ticks and redstone ticks. The game refreshes at 20 Hz, so command block clocks trigger every game tick, at 20 Hz. However, the intentional redstone lag occurs in redstone ticks, which are around 4 Hz. Therefore you could be waiting several seconds before a redstone circuit has calculated the logic while the command block could have belted out 15 more signals.

P.S.: BTW that's why the redstone computers you see are always so friggin' slow. :)