Because Discord isn’t just for friend groups, it’s also for large open-entry servers open to the wider userbase. Slack-based/group chat alternatives completely lack this.
Bringing in age-ID verification that they had to apply in the UK and Australia globally for all accounts to access NSFW channels and to be able to take the baby filter off of DMs.
They got heavy backlash for it, and have now delayed it.
Slack is also paywalled to a laughable level.