Can't speak for Slack, but Discord is a fully walled garden, and they make sure to control how content on the platform is consumed. You can't automate your own

Can't speak for Slack, but Discord is a fully walled garden, and they make sure to control how content on the platform is consumed. You can't automate your own account in any way without risking a ban due to breach of ToS (see "self-bots"). This makes it impossible, for example, to get local chat logs (as the official client doesn't support it).