Ticks have too much speed, damage (when factoring in flanking bonus and the sheer difficulty of cleaning all of them up) and don't leave wrecks. Something must be done.
If the engine can support scrap being combined then a giant tick ball could leave something worth killing them. The sheer amount of overkill from killing ticks means nothing is left for a defender to salvage.
They have great vision too, which fits being a scout unit- but makes them a bit too effective when paired with their unparalleled speed.