A 1TB SSD drive costs around 100 (€/ $). A person who enjoys tweaking their PC likely can easily get terabytes of storage space. I don't really see the utility of fiddling with 10GB here and there...
So yes, 10GB here and there isn't much.. but as a collective, if you have 1000000 users downloading 300GB less per month (I know, silly numbers, it's way more in reality), it would make a huge difference to the "gaming industries & network load"-effects as a whole. Plug-in some real numbers (which I don't have)(Players X ave number games downloaded per year X ave game size).
Other industries like streaming/music sites, they optimize their transmission sizes and even small gains are often worth it (10 million people downloading 2MB less per song on spotify, while playing 50 songs per day... the numbers add up quick). Somebody will pay for the transmission - either the consumer or the business. The business only needs to ask is it cheaper to pay a few devs to optimize their code or is cheaper to pay for a fatter data pipe. I think long term, engineering effort always wins vs throwing money at the problem.
I have a bog standard internet connection with a download speed of 1000gb. Most games download faster than it would take me to go to the store or order a package.
I really like Nintendo Switch cartridges, I prefer to buy physical copies when I can, but I don't think there's a future in them. I kind of wish someone would make "smart cards" that just gives you access to the game online. Since there's so many essential updates to games these days, that's almost what cartridges are anyway.
You forgot the reference link btw.
That would be terrible from an archival perspective. Flash memory is subject to charge leakage that causes data be lost over time. High density flash, which has the lowest cost per byte, also has the poorest data retention lifetime.