On a large chunk of Enterprise Software you'd have teams of people working on specific features / subsets of a larger product.

I.e. a team that is working on only Facebook Messenger back-end, a team working on Facebook Messenger Front-end, a team working on Friend Recommendation, etc.

Each of these teams is let's say 10 Dev, 2-4 QA, 1 Product Documentation, then all the normal overhead of HR, etc.