Why is the time so short for leaving a game and claiming victory?

I think it's very unsportsmanlike to claim these after thirty seconds or so and doesn't give people enough time to reconnect

@DangerCat : I think it's proportional to game length. Not sure though.

@DangerCat You can claim victory after 2 minutes the opponent left the game and I think it is not too little time to reconnect.

I don't see a reason to allow a player to claim a victory when their opponent is having connection issues. You don't allow it if the opponent is thinking (or stalling) for two minutes either.

@MessyAnswer Well I think they implemented this because of people leaving the game on purpose or because they have to do something else at the time and probably won't reconnect within 10-15 minutes. It would really be terrible though if you had to wait for your opponents time to tick down to zero in a classic game that lasts like an hour so it's probably better this way.

Some of my opponents will disconnect a lost game instead of resigning. When that happens I'm glad I can claim a victory immediately.

When a player (X) disconnects for whatever reason, it's difficult for his opponent (Y) to keep concentration because Y doesn't know X would come back or not. This gives X unfair advantage if he does intend to reconnect. In my opinion, disconnetion should be a loss immediately, though Y may allow some grace-period as an option.
At the moment, Lichess's handling of the issue is a good compromise I think.

Its a two way street. My position is that if you have a poor internet connection or trouble with your computer, it is your problem. Fix all your internet issues if you want to have a pleasurable online chess experience instead of ruining others' online chess experience with your interent problems.