That happens to everyone at the start of the season, it is trying to show realism in the game, the best player on a certain level may not be the best on the level after, that is not the main reason, that is top eleven’s explanation for it anyway.
For me.and for everybody else, without the quality drop, it would cause teams to become way too overpowered, which would defeat the purpose of auctions and all areas where you can buy players.