Again this has been explained many many many times.

The most easy and all round meta team any player, f2p, p2p and p2w can get is the mei-tenten-mabui team. Other than having more initiative than them to shut mabui/mei, steal the barrier and kill mabui turn 1 there is no surefire counter, or team that can kill them reliably (DP Hidan is a tad too expensive to be considered a viable counter for the majority of the playerbase).

Hence, most people will use such a team in order to win some matches in matsuri. Specially since many of the players get matched with higher BP opponents fairly often and meta teams like this one are the only ones that can give them a shot at winning.

It does get boring to fight the same teams overall, but the truth is there are only so many viable meta teams atm. As time goes on and more Roshis and Hans get pulled things may change, but atm the mei kage setup is still the easiest to get.