If by "scares" you mean manufactured, misleading hyperbole, you're wrong. There are tens of thousands of adverse drug interactions annually in the UK (and more in the USA). Many of these are avoidable (they're not just drug-drug interactions, adverse drug-condition or drug-{age,procedure} interactions occur too) and key to avoiding this is delivering timely, accurate information to your healthcare providers.
Keeping yourself off the relevant clinical databases is a choice and a compromise of risks; on the one hand the risk that your data will be leaked and on the other hand that your choice to equip your clinicians with less information will cause you to get less effective treatment in the future.
In some senses this is a balancing of benefits to do different people; first, your healthy, vigorous, young self. Second, your elderly, sick, incapacitated self. The latter cares most about the privacy angle but I'm pretty sure the latter cares most about the quality of care. But it would too late for the elderly you to benefit their treatment by reversing the decision made by their younger self.