user12730: I have encountered a profound number of players that simply leave the game when they realize they are losing/in difficult situation, without pressing "I resign" button. This often leaves me waiting a long time for no reason and, consequently, wasting my time.
Is there a site that prohibits this?

user13119: Use lichess.org. When your opponent leaves game you can press button 'Claim draw/loss' there

user12540: Chess.com has an algorithm which senses whether a user/player is active or not during the game.
I am not very sure but they have a time frame of 5 minutes, during which if they find the player is not active then the game gets abandoned and the opponent wins. 

12730: <p>I have encountered a profound number of players that simply leave the game when they realize they are losing/in difficult situation, without pressing "I resign" button. This often leaves me waiting a long time for no reason and, consequently, wasting my time.</p>

<p>Is there a site that prohibits this?</p>
 13119: <p>Use lichess.org. When your opponent leaves game you can press button 'Claim draw/loss' there</p>
 12540: <p><strong>Chess.com</strong> has an algorithm which senses whether a user/player is active or not during the game.</p>

<p>I am not very sure but they have a time frame of 5 minutes, during which if they find the player is not active then the game gets abandoned and the opponent wins. </p>
