TOCs can only lose money proportional to how bad their service is. DR needs to be punitive in order to give TOCs an incentive to improve their service. The system needs to be easy and fair, even if it opens up the possibility for bad people to commit fraud.
Delay Repay is far more generous than most schemes elsewhere. In Switzerland, you need to be delayed for an hour to claim just 25% of your ticket price back. The same in France, Sweden and Italy. I could search for more. Try getting money back if your flight is 45 minutes late (or even, three hours late if it wasn't the airline's fault!), or if your bus is late.
I would personally abolish all delay repay schemes and replace it with a scheme similar to EC 261 which applied to the airlines, with fixed payouts and only for the most severe delays.
Delay Repay is a big hobby horse of this forum but almost no normal discretionary passenger chooses the train based on the idea that if it's late they'll get some form of refund (which they usually have to claim anyway). They'd prefer not to be late in the first place, and the vast majority of passengers that travel every day aren't delayed.
Delay Repay on season tickets is an invitation to, at best, gaming the scheme, and at worst, outright fraud. There's not a compelling reason to have the scheme; it's more expensive to administer than the cost of the compensation, and it makes very little difference to passenger choices.
If there weren't so many delays, there wouldn't be the any opportunity for scamming.
Seems to me to be victim blaming.
The problem with scamming is that Delay Repay is already extremely loose, and is effectively treated as an honesty box scheme. If I have a paper Off Peak Return from London to Manchester there really is no way for the TOC to be satisfied I travelled on the 1100 train I claimed to have done.