This can allow you to cheat in some ridiculous stuff for Bant mana, like Portal to Phyrexia in Commander, or rather unflavorfully, Doctor Octopus, Master Planner
Sometimes there are also special events where you can also win ICRs
With how much stat-boosting goes on, it becomes very easy for Amy to hit that threshold
For example, if you put Spellbook (an artifact that says you have no maximum hand size) onto the battlefield and then put Doctor Octopus, Master Planner onto the battlefield, your maximum hand size will be eight
Most of the best utility lands enter tapped, but not Three Tree City, and even if you don't have the right creature types, you can still tap it for a colorless mana so it's not ever sitting around doing nothing
These are typically green cards since green is the MTG color most associated with the power of nature, mana abundance, and lands