Blu-rays do not actually take up this much space: On a 1TB drive you can store about 10-12 4K movies. You need a backup and you need a second drive for your Raid setup. This takes up quiet a lot of space too.
Besides that: storing the movies on a Raid system is a lot more expensive. If I'd rip all of my blu-rays to a digital copy, I'd need like 12 TB of storage. In a raid setup with backup, that's quiet expensive!