It's about technical capability. In this case, Discord is a very centralised service. They store all of the messages centrally, so can easily comply with the r

It's about technical capability. In this case, Discord is a very centralised service. They store all of the messages centrally, so can easily comply with the request. Other services like email may not be able to do that, so they could use that as a defence when asked why they aren't deleting all data.