A better question, and one that gets to the heart of why Blizzard's CEO is overpaid, is why do they need 10k people to make, distribute, and support a few video games?
There are far, far more effecient video game studios/publishers out there.
Nintendo manufactures and ships millions of hardware units in addition to producing/publishing games and they have fewer employees.
That is, in fact, why blizzard just laid off 800 people- they were from underperforming sections of the business or, iirc, business they wanted to get out of.
"Underperforming sections"? Customer Support rep which gave it his all got fired. Due to such people getting fired there's going to be a gap between community and company. How can that possibly be an "underperforming section"?
Because it takes a ton of people to offer support on video games. If you have millions of monthly players then you need a lot of employees to manage the community.