Some statistics.

Another alternative to using explosives: position your units tactically, use mass haste, and charge forward.

This requires many conditions. Mass haste (which isn't always available, or there might be a lack of haste or expert air units). The first turn and the absence of high-speed units from the opponent that would allow them to perform a mass slow after the attack of 1-2 units. Also, for example, it's good if you get the tactic skill while your opponent doesn't, but what if it's the other way around?