As far as I understand the point is supposed to be the blockchain is distributed trust. The longest chain = proof of most work = the truth. The only reason someone can't basically change the entire history of the blockchain is because no one has 51% control of the chain. The only reason no one has 51% control of the chain in bitcoin is because so many people are mining it to earn coins.

But, for medical records there is no such incentive. Therefore anyone can easily change the records or add new ones and claim everyone else who has a shorter chain has the wrong chain (which will be like no one since there is no incentive to mine).

So I'm probably just informed how blockchain is supposed to help here. Without the distributed trust there's no plus to blockchain. And without the incentive to mine that generates millions of miners there is way to have the distributed trust.

I'm happy to be wrong but I haven't see an explanation how this issue is solved for all these non virtual currency uses cases.