When an ally rage quits/afks/disconnects

So everyone has had their games when an ally champion decides to either AFK, rage quit or disconnect leaving your team with a 4v5 and almost always a loss for your team. I understand this is something that is not really avoidable and has been somewhat controlled by punishments but regardless to what ever happens to this persons account afterwards is actually irrelevant to a player who is trying to climb. I don't need justice on someone who has dropped my LP.

Now with that being said I would like to know a logical reason to why when the game ends in a 4v5 that still had great potential to get a win the 4 players who stayed in the game to fight lose the same amount of LP that would have been lost from a 5v5. Now I'm not saying this as it is the reason why I'm not in a higher elo but I will say that it is very upsetting to be set back due to other peoples issues. Why is it ok that we still lose the same LP and have to play another 20-60 minute game to gain back what was lost again due to someone else's issue.

So I am curious to why something that seems so unrealistic has either not been fixed to result in a more considerate outcome for the ones who stay dedicated or if this has been noticed by Riot... What is the reason that this can not be fixed? Thanks for your time!

Your typical upset silver summoner