Yes, if you could 100% guarantee that someone was going to have a $Y valued claim, their premium would fairly be 100% of $Y at least in order to allow for their contribution to the risk pool. Problem is, you cannot 100% predict the future, and there is no model capable of doing so, nor will there likely ever be. Nor can you predict that any other insured risk might not materialise in the meantime.
More to the point, it fundamentally misunderstands what insurance is and how it works, not least the commercial considerations involved. If there is a 100% risk of risk X materialising, the insurer won't rate your premium at the cost of risk X; it will simply exclude risk X from your policy and rate your premium based on all the other myriad risks that might arise that year in an attempt to win your business and collect premium for what, to them, is a better bet.
This already happens, incidentally; travel insurance policies will exclude pre-existing conditions or recurrences of previous illnesses as a matter of course, because if someone (e.g.) has cancer, the odds of them needing to claim on their policy - and as such draw down from the pool more than they paid in premium - skyrocket.