They are more expensive to mass produce.

Because some people actually ENJOY having hard copies of beloved films, and lament the systematic elimination of the album art form

SSD's are not produced in bulk. They are a little too complicated and expensive for that. You just need to read up on how SSDs work.
But let's look at this logically. They cost roughly around $0.10 per Gigabyte (And since movies series and TV seasons would be several hundred Gigabytes you can do the math) to produce.
Meanwhile it costs $0.06 Per Gigabyte roughly to produce a 50GB Dual Layer Blu Ray Disc. Which to some might seem like negligible. But those 4 cents add up quick when you're producing thousands upon thousands of discs or drives.

Unless you find a way to streamline and cheapen the production your little idea isn't going to sway any film studio to go along with it.

Also let's not forget there's nothing wrong with Blu-Rays or DVDs. They work fine. Fairly priced. Unlike Laserdiscs they aren't fucking huge, and unlike VHS Tapes they don't slowly destroy themselves from use and run at a quality higher than 480i. No point in reinventing the wheel when it'll just raise prices for no reason.