Imagine you want to track eggs through the supply chain from farm to table. Ultimately the trust of your system is rooted in the farmer and various other organizations that are updating the state of these eggs in the chain. If they make up fake data, the system isn't trustworthy.
Typically the solution for this is to only let trusted players into the system and have some sort of organization - perhaps the government - that vets users of the system and penalizes those that enter fake data. In this case, the trust of your blockchain-egg-supply-chain-tracking system is rooted in the organization accrediting and inspecting users of the system. If that's the case, you're better off trusting that organization to run a traditional database. You shouldn't use a blockchain.