Most if not all train operators in Great Britain offer Delay Repay regardless of the cause of delay or whose fault it was. (If you feel it is morally wrong to benefit from another passenger's illness or the like, you can choose not to claim, though in some cases if you have an online account from which you booked a ticket, it may be automatically paid).

I can certainly see some advantages to making airlines pay compensation regardless of the cause, perhaps with some adjustment of the amounts. It may be more efficient to have large companies take out insurance to cover compensation claims from external causes, rather than having hundreds to thousands of passengers fighting individual battles with travel insurers.