LPQ is typically gotten for repeat offenses, and is therefore directed at people who intentionally AFK during a game for malicious reasons. Unfortunately, Riot cannot determine why you left a game, or what circumstances happened to you, so they have to resort to this measure, as regular AFKers cannot go unpunished. So, if you believe that you'll need to do something in the next 20 - 60 mins then don't play the game. If you have regular power outages don't play. If you have a family member in the hospital who you may have to go to at anytime then don't play.
Now, for unforeseeable events (relative fainting, fire starting), the first offense won't usually result in anything. Multiple offenses usually means that you, unfortunately, shouldn't be playing a game that takes 20 - 60 mins per match. Usually this can be avoided by asking your parents if they have anything that they'd like you to do, or if you live alone, ensure that the house is safe so no emergencies happen.
If, for whatever reason, you are always being interrupted, then play a MOBA that has a shorter average game length, such as Heroes of the Storm, Battlerite, Overwatch, or Paladins.
Although you may see this as 'just a game' others may not, and may have a limited amount of time to have fun and you not ensuring that you will be unlikely to have to leave when starting a game, or starting a game when you know you can be called can result in the small amount of time they allotted to go to waste, by playing a losing 4v5 rather than an 'even' 5v5.