There are obvious responses here along the lines of embracing piracy and (re-)embracing hard copy ownership.
All that aside though, this feels like a fairly obvious point for legal intervention. I wouldn't be surprised if there are already existing grounds for legal action, it's just that the stakes are likely small enough and costs of legal action high enough to be prohibitive. Which is where the government should come in on the advice of a consumer body.
Some reasonable things that could be done:
Money back requirements
Clear warnings to consumers about "ownership" being temporary
Requiring tracking statistics of how long "ownership" tends to be and that such is presented to consumers before they purchase
If there are structural issues that increase the chances of "withdrawn" ownership (such as complex distribution deals etc), a requirement to notify the consumer of this prior to purchase.
These are basic things based on transparency that tend to already exist in consumer regulation (depending on your jurisdiction of course). Streaming companies will likely whinge (and probably have already to prevent any regulation around this), but that's the point ... to force them to clean up their act.
As far as the relations between streaming services and the studios (or whoever owns the distribution rights), it makes perfect sense for all contracts to have embedded in them that any digital purchase must be respected for the life of the purchaser even if the item cannot be purchased any more. It's not hard, it's just the price of doing business.
All of this is likely the result of the studios being the dicks they truly are and still being used to pushing everyone around (and of course the tech world being narcissistic liars).