No one seems to grok the real question here: "Why does Goldman Sachs automated trading still need 200 engineers?". What are those engineers doing? And why will

No one seems to grok the real question here: "Why does Goldman Sachs automated trading still need 200 engineers?". What are those engineers doing? And why will they still be needed in 5, 10, or 20 years? Where are goals created and trading decisions made? How are automated trading systems going to evolve? Once working, will automated trading systems need regular replacement and upgrades to protect them from bit rot?