To remind you that they shouldn't be put into your regular deck, they have a unique card back
The fact that this card gets flying after growing makes it an excellent choice for a low-cost beater, and it has great synergy with cards that spread +1/+1 counters on others like Ouroboroid or white planeswalkers that make tokens and give +1/+1 counters to all creatures (Elspeth, Ajani)
Just a couple dragons can win the game fast, and this is like Tooth and Nail entwined for Dragons
This is a great card for control builds that benefit from having ample spells as well as one or two Planeswalkers with which to defend themselves while they slowly etch their path to victory
Lifegain strategies are among some of the most popular ones in any format, and Commander is no exception
This begs the question, which cards and legends make the best MTG Commander decks