But they simply don't care.
In the past before computers they would be putting these in files on a large file folder shelving units with colored folder tabs behind a counter and the only real security was a receptionist that would stop you if you tried to interact with it, and they locked the door to the office when they left. If someone broke into the office back then too, your medical records would've been stolen & unencrypted (beyond the illegibility of most doctor's handwriting) and as a society, we were ok with that security level.
Harsh fines are probably the best way to make doctors care though. If they know they risk financial ruin for not securing their records, they'll have a strong personal incentive to remediate their ignorance.
For all you know, they could have had that system too, the article does not say what it was.
BD-R (except LTH) use an inorganic layer to record on.
Now they should be doing 3-2-1 backups. With S3 they'd be paying $160/month (for storage, not counting other costs) for 8TB or $40/month for BackBlaze B2. That's 8,000 customers.
They're in England so some variance in pricing. But it would be relatively inexpensive to buy big drives, sync them to a set in the office, and back them up online. Where the doctors or whoever is running the clinics can SEE the data is still there whenever they want.
I agree that there should be increasing worry about keeping information that you don't need, whether it's intimate pictures of your surgical clients or people who bought from you 5 years ago and not since. But it seems like keeping things handy will be an impulse that's hard to overcome.
(which isn't to say that they'd purposefully choose two different implementations. Rather, just that if i'm using poor person doctors i'm unsure they'd rise to the new "standard" of security practices)