Even on gigabit, many AAA games are over 100GB these days. That's big enough to get annoying. My personal system has 4.5TB of SSD and 8TB of HDD (Used for backups, etc), and that sometimes doesn't always feel like enough - and I'm not even doing video editing or anything.
No one is playing triple A games on a HDD anymore though. I did the math and found it was about the same speed to redownload from steam as it was to copy a game off the HDD.
