Why is a subscription required for Peer to Peer?

Well, ”Sony requires PS+subscription only for games that connect through peer-to-peer (or don't have their own dedicated servers). Since fortnite has its own dedicated servers, it does not require a subscription.”
and it's different from how the Xbox subscription works. Hopefully, sometime in the future, it will be possible.

For suggestions like this, you'll want to post at http://xbox.uservoice.com

ITs Peer to peer thats why is so laggy at times.

Wow, even I have a better understanding now. Thanks, OP!

Ping and Latency is how the matchmaking works, so in theory, everyone should have about the same connections. The Upload is the biggest part of connections for gaming but it does make sense that the lobby is only going to be as good as its slowest occupant,
but I am not positive. I also believe the lag comp was added into gaming to ease the Godmode host that host used to have and they (the devs) try to even the playing field, so to speak by adding some delay in the connections (however minute) but I think it
kinda fails. I mean I do have great games with great connections alot of the time, but "in general" people complain of the lag. It is what it is.