Read what you wrote.
Blizzard provides a bonus roll and people twist it around until it's mandatory. Go look up the definition of 'bonus'.
It's perfectly true that peer pressure from your guild may have made them mandatory. Guilds in server 10-ten races may have made them mandatory. That's a people problem, not a Blizzard-makes-us-do-this-when-we-don't-want-to problem. And SamR has it right. Pet Battles are an entirely low-stress and easy way to get the coins.