I think you're confusing cause and effect - 1-2 TB is the most common for PS5s because it's still where the price-per-GB sweet spot is. I bought a 2 TB because it was the cheapest per GB at the time, figuring I'd come out ahead financially even if I replaced it with a 4 TB in 2-3 years.

Alas, prices have not come down like I expected. And sure, there's only so many I can play at a time, but I also don't want to have to wait through a reinstall each time I change it up.