JIT in farming has obvious problems. Say you have a sick cow and have run out of the drugs needed (you have used them or they are out of date, and you did not know you would need it), so you nip down the vets, get a bottle (and a new needle!), nip back to find the cow considerably worse. You have to get the vet. You now have costs of time off farm, transport costs and vet costs.
Or like me, you have a tub of plumbing fittings that have cobwebs in them. A pipe splits and the right fitting is not in the tub. So you nip down....
We cannot foresee what calamity is going to hit us next. We are not fulfilling regular orders of stuff that does not die, go mouldy or a mouse poops in it.
So we tend to hord stuff in barns that "might come in" and quite often it does. An old tube for a cluster can be used for a split pipe to quite good effect.
And this is , very much, the reasoning why JIT can`t work in the NHS. If there isn`t standardisation/stability of both input & output JIT can`t work well & will create more issues than it fixes, we aren`t making cars...in our case we are looking after sick folk, in farmings case its weather, stock and many other things. Both industries have too many variables and the only thing that gets you through is experience & knowledge.