In the last gen mandatory HDD installs were the exception, not the rule.
Most Xbox 360 and PS3 games had to load most of the data from the optical disc (DVD or Blu-ray):
The Xbox 360 had a 12x DVD drive, so sequential max. speed 15.8 MB/s with abysmal seeking speeds compared to 5400 rpm HDD.
The PS3 had a 2x Blu-ray drive, so sequential max. speed 8.6 MB/s with abysmal seeking speeds compared to 5400 rpm HDD.
Last gen already relied on HDD, installing bits and pieces or using the HDD as cache. Plus last gen actually had tricks to use both HDD and optical drive together. The digital version of Halo Reach actually performed worse with only the HDD to run from instead of using both pathways.
So actually we went a bit backwards this gen in general I/O since everything is installed on HDD now, no more benefits from a secondary source.
Sorry, but you are wrong. (Or I'm dreaming I had to wait 10 minutes between MGS4 chapters to install the next part to HDD)