What drives growth of custodial & non-custodial wallets, and what is Kraken's view on the custodial vs non-custodial debate?

Once upon a time, the only wallets were non-custodial wallets, and the user experience was challenged on a lot of those. 

Then came the first custodial wallet—and afterwards, the exchanges which provided an on-ramp from fiat to crypto. That on-ramp is often easier to do through a custodial offering, much the same as fiat. 

What we're seeing now is the non-custodial wallets improving their user experience, and that's fantastic. This almost goes back to a little of our discussion on decentralized exchanges: using Bitcoin and crypto in a non-custodial way is the purest way to use crypto. 

At the same time, there's a ton of value to offering a custodial and off-chain experience, particularly if you're interacting with the fiat ecosystem. We really think both are the future and we hope that non-custodial usage continues to grow significantly.