Ask HN: Why can't Gmail auto-delete "100% certain" spam?

Sometimes I look in my Gmail's Spam folder and see 100+ Russian emails that are all spam. Why do these even get to me? It makes no sense - they are all 100% spam.

Google surely has algorithms that can show them that 200,000 almost identical emails were sent during x minutes from the same IP. They have the technology to detect it as spam - so why not just auto-delete it? What does Google gain from me even having the option to see these emails?