Most of what the teams do at a competition isn't actually on the playing field but for what is done there it's largely run by human operators in real time from control computers connected over Wi-Fi so you can't really send the bots without sending the team.
A related anecdote: I seem to recall a team from another country (Israel?) not being able to attend the world championships, but they were able to send their robot, and coordinated with another team to have that team operate the robot.
But yeah, a match is 2.5 minutes; and only in the first 15 seconds is the robot is entirely autonomous, for the remainder of a match there's a 2-person drive team (plus maybe a coach standing behind them) operating it over WiFi, and also a human player that is able to interact with the field from the sidelines. Nevermind all the activity in the pits, repairing and adjusting the robot.
