The 1v1 map pool has 7 maps and each player gets 3 bans. If both players ban 3 different maps that leaves 1 map for them to play (7 - 3 - 3 = 1).
The team map pool has 9 maps and if 2 players queue up for a 2v2 each team gets 4 bans. If the bans are all different that leaves 1 map for them to play (9 - 4 - 4 = 1).
They same applies for 4 people queueing up for a 4v4 (4 bans per team), however when 3 people queue up for a 3v3 they only get 3 bans per team (leaving 3 possible maps).
Its not the biggest problem but it would be appreciated if we can get 1 more ban per team in 3 people queueing up for 3v3s.
(edited formatting)