The PPS pools act as a "reserve" for them, but that comes at a price of higher pool fees and the possible loss of the money "in transit", in case they get "hacked" or the pool it does not (really) have the proper reserve to withstand an extended bad luck period (or a combination of).

I guess a day/week loss of payment for a single asic miner isn't much to worry, but the whale miner would lose a fortune. Ironic they rather take the risk than learn to manage themselves. If the PPS pool fails a payment, then they would fail with it. Essentially you are trusting the pool like you would trust a bank, hope they can keep that "reserve" safe... And how can you audit if your PPS pool has the appropriate reserve levels?