It's because we can't offer a fee greater than 1 satoshi pe…

It's because we can't offer a fee greater than 1 satoshi per transaction through the SHUAllet integration at the moment. And when the network is loaded with tens of millions of low-fee transactions like that per day, a lot of them end up unconfirmed. I've noticed the transactions typically disappear after 7 days if they don't get confirmed into blocks.