Storage space is at a premium. The PS5 has about 650gb of usable space. At ~100gb/game which is not uncommon you can store 6 games on the console without needing to free up hard drive space.
Filesize matters, especially to people with limited bandwidth and data caps. The increasing cost of SSDs only makes this situation more hardware constrained.
Do you have six games you are actively playing? That is more than most. And 100gb is not an average to my understanding sure there are AAA games that go over that but it isn't like you need to swap between a bunch of those. (Also they tend to be set piece so not something you go back to)
Again I agree optimization is good just pointing out it tends to not impact people. "My default driver can only handle six full game downloads" isn't actually a blocker to most people playing a PS5.
Filesize matters, especially to people with limited bandwidth and data caps. The increasing cost of SSDs only makes this situation more hardware constrained.