Teambuilder: Create a team? Invite a friend! ...why?

I'm curious as to why this decision has been made. Why does creating a team in teambuilder now requires one to invite someone else, while no other modes ever require that? Honestly, I find it rather... limiting.

You might think.. "eh, everybody has at least one friend they play League with, so what's the big deal?". The big deal is basically that I haven't seen any real reason given, other than "due to popular demand", which is rather vague. Why do apparently so many people want this? And why only in Teambuilder's Create a team? Why is going into matchmaking alone fine in every case except this? Even Ranked has a solo/duo queue, no partner or team is [i]required[/i].

I'm assuming it has something to do with the new SR updates, but the context of the announcement in-game didn't really state if it was temporary or permanent.

Bottom line... I'd just like to know why this decision was made, in detail if possible, and whether it's permanent or not.