Imagine 2 people are playing. Player one is up 2minor pieces. Then, player 1 blunders a queen. Boom, now player 2 is winning and player 1 is losing. If lichess auto resigned, then player 2 never would have been at an advantage.
Edit: stalling against the timer will result in a temporary ban, lichess already took action on that.
Edit: stalling against the timer will result in a temporary ban, lichess already took action on that.