Answer:
Because they can't!
Step-by-step explanation:
For ionic bonds, ions are needed to be made which are made to form a stable outer shell octet of electrons of each atom to gain atomic stability. The noble gases don't need to form ions since they already have the octet of electrons in their outer shells. If they don't form ions, they don't form ionic bonds too.
This is one of the reasons why noble gases are unreactive.
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