Why do we get punished so hard for loosing an autofilled game????

So tonight i wanted a quick match before night time qued up mid / jungle get one game get mid want to play viktor . after champ select a guy dodges meanwhile some whiny guy wanted to play adc didnt get his role so he picked trynda supp right so the next game comes up i accept the game i get autofilled support im like aight i suck support but whatever cant afford to dodge right now so i go with it . Than the guy locking in trynda as support gets his adc role so he plays cait im like ok im gonna play brad (bard) because dude is hella fun we end up loosing the game because cait trolls and flames . meanwhile i am stuck on a roll where i cant be the starplayer (i could if i practiced it but i didnt). but yet i get hit by the full punishment of loosing while if i mgiht have jungled i could have done so much more and i actually feel like i lost but in this case 15 lp straight thru the drain. so my reasoning nobody wants to be support or whatever roll they get filled they probably arent familiar at it at all like i am with support and adc they accept the to play the game hoping for the best (also more or less forced to play the game due to loosing 6 lp while you are at the brink already) it isnt the right reward for wasting time at not having fun that certain game . so why not cut the lp loss in half for players who just get thrown before the wolves you know treat your players right and not make the game saltier than it already can be.