You have to be level 57 to participate in 3v3, sorry about the confusion.

I understand why you feel like that, however most things are level-gated to an extent, most at lower levels though. Level 57 is still quite low compared to other things that are unlocked later. Many games unlock new skills or systems as players level up.

I am not sure what their reasons were exactly, it is not something I am privy to, but my best guess is, most lower level players do not have access to enough characters to make a team that can battle against many of the other longer standing players who participate in the system. Any guesses that I come up with, would just be hypothesis though.. However, I do think it is a good suggestion to lower the level restriction on 3v3.

I am not sure, I can ask, but I do not know if it was intentionally removed.