By powering one up, your opponent is basically telling you you have to deal with this, or you lose. This is why, if your opponent has a Lycanroc-GX with enough Energy to attack, the best course of action is usually to either two-shot it or one-shot it with your own Dangerous Rogue GX
Most of the top-tier Commanders there are Partner combos, and many of those make use of Tymna as one of their picks
Landcycling also triggers Rielle, the Everwise to add regular cycling to your landcycling
Tapping a creature thats equipped doesnt tap the equipment attached to it, and tapping an equipment doesnt tap the equipped creature
They can simply be used for better mana in some decks while other decks rely on them to work
In a deck full of small creatures and control elements, its not hard for this cutey to be a two mana 5/5+ reminiscent of the once-100 card Tarmogoyf