If we look at the most played creatures in the 99, this hits Archmage Emeritus, Champion of Lambholt, Drannith Magistrate, Esper Sentinel, Grand Abolisher, Notion Thief, Opposition Agent, Pitiless Plunderer - the list goes on
However, if you skip attacking after playing him, the buff is wasted
You can challenge your opponent and eliminate (banish) their cards that are in play to limit their opportunities to gain points
A monster that is treated as an Equip Card is still treated as a monster and therefore can be used for something like Ritual Summons
Zirda requires our commander to have an activated ability (along with every other permanent)
Many decks play Abilities, like Genesect V [Fusion Strike] in a Mew VMAX deck, and they rely on them a lot too