In a perfect world the entire computer, storage included, would run in RAM for performance reasons. There's actually been some storage products over the years

In a perfect world the entire computer, storage included, would run in RAM for performance reasons. There's actually been some storage products over the years that were basically RAM chips with battery backups for when the machine turned off, but they never took off due to implementation issues/expense, and then SSDs got big and fast enough for 99% of use-cases. Plus we're just victims of our own technological success. RAM is cheap. Similar to all the old classic cars from the 60s, gas was cheap, engine tech advanced and environmental regulations nonexistent, so you got giant 7L V8 engines running at like 10 mpg even with premium, leaded gasoline. It wasn't until pollution regulation, gas taxes to pay for infrastructure, and now climate change (in some peoples' minds) that efficiency became a priority.