Crew and saddle keyword abilities mean that youre tapping creatures to animate vehicle artifacts and to improve your mounts performance, so youre always turning a bunch of cardboard sideways in these kinds of decks
I WANT to pay attention, I do, but some people's brains don't love that sort of prolonged concentration and yearn for outside stimulus
Heat Shimmer is great, as not only can you copy a creature for their enter the battlefield ability, but it can also combo with Dualcaster Mage for an alternate win condition
If your opponent only has 10 blockers and youre attacking with 20 creatures, theyre toast
He gives you a bunch of information, lets you do disgusting green ramp things off of the top of your deck, becomes a giant monster....what's not to love
This has a passable baseline as a three mana 2/2 that can tap for Green, and most Green decks in this format will have enough Elves for there to be additional upside