The server owner decides this and if you have a somewhat big server you want it enabled. I guess you could blame Discord for not having better spam prevention and toxicity filters but it's not an easy problem and I presume they catch a lot we don't see.
> The server owner decides this and if you have a somewhat big server you want it enabled.
I am not talking about servers requiring phone numbers, I am talking about Discord blocking your account entirely for no reason until you give them a phone number. Maybe you haven't experienced it yet, but I have.
The only times Discord has asked for my phone number (and I have many alts) is when a server specifically says that only people who have added a phone number to their account can join. This is off by default.