If there's a cost associated with having it attack, its controller isn't forced to pay that cost, so the creature doesn't have to attack in that case either
More importantly, you'll notice a trend if we look back at flashback and other split cards: to make the cards fair, Wizards tends to increase their mana cost or ever so slightly decrease the effect of the card
Furthermore, pulling the featured cards becomes crucial for the game's battle modes, so players should look to acquire them as quickly as possible
Tinybones, the Pickpocket
The ability sounds great, but with the 0 Strength Jafar can be removed by Ruby easily
We just had a rare emergency banning to remove Field of the Dead from the format after it made up 43% of the metagame at Mythic Championship V, and now we're heading into Mythic Championship VI with Oko, Thief of Crowns approaching an unprecedented 70% of the Standard metagame at some recent tournaments