Many cards have Shift or abilities that rely on certain types and numbers of characters being in play (we're looking at you, Seven Dwarfs)
The transformation doesn't necessarily make the card more powerful, but it maintains Flash, adds Double Strike, meaning you double the damage output in combat, and shifts the card draw from opponents drawing two cards per turn to combat damage dealt to players
Green is especially great at destroying things that aren't creatures
Appearing exclusively as tokens, and boasting humble 1/1 stats, these fungus-based lifeforms have nevertheless received consistent support throughout the games history, making a dedicated Saproling deck not only viable but potentially extremely powerful in the games premier multiplayer format, Commander
Because I just want to troll opponents by gifting Dralnu to someone right before he takes tons of damage and make my opponent sacrifice those creatures
However, for your combat damage to get through, you will need some protection from your opponents after they have either saved up the mana to blow away some of your Humans or kept some of their poor creatures untapped to block you (even if your creatures can't die because of Goldbug, Humanity's Ally )
