If your game is crashing so often that you get punished by LeaverBuster, then you might want to try doing something to fix that. New computer, uninstalling/deleting no-longer needed files/games/apps, using a usb stick to keep large projects on if you have any, or anything else that could help. Lowering your in-game settings all to low and turning off shadows and eye candy could help as well.
If Riot made a system that asked you why/how you left a game, everyone would say "family emergency", "power went out", "computer/laptop bluescreened" or anything else that we can't really control all to avoid punishment. If you know your computer can't handle League, don't play League. Leaving every now and then is one thing, but leaving so often LB gets you is another.