If you don't have the 20 minutes to commit to the game, then you take the penalty. Yes, there will be those times when you have to leave because the cat is on fire or the FBI is at the door. And in those instances, a 30 minute penalty isn't a big deal given that you probably put the cat out after 15 minutes and the FBI goes away after 20 - so your penalty is really like 10 minutes long.

And it protects the rest of the playerbase from this being abused.