Why insurance claims such as airline strikes etc. not covered in policy?

[White Caps]

I am asking when the insurers provide coverage to -
1- Trip delay, cancellation and interruption
2- Hijack Distress Allowance

Why not to airline strikes and acts of terrorism?

Insurance works through the magic of the law of large numbers. This law assures that when a large number of people face a low-probability event, the proportion experiencing the event will be close to the expected proportion. For instance, with a pool of 100,000 people who each face a 1 percent risk, the law of large numbers says that 1,100 people or more will have losses only one time in one thousand.
Insurance premium is calculated with the help of past data and insurance company include that only if large people are interested to cover that risk and it is profitable for them in the end. So may be insurer have not much data or not interested to cover it or may be premium is very high.

[RyanD]

You can take comprehensive travel insurance in good company. It have rather good cover, but its price isn't cheap.