Level 30 first gamed ranked, always put in silver?

So I am aware, S4is about average and so when you hit level 30 you are basically given an mmr to match that. What I don't get is why they can lose 5 games in a row and keep being placed with this elo with people who are trying to climb. We can't be expected to carry them all the time when they just hit 30 and go a champ they have no idea how to play. Why aren't they placed with other recently ranked 30's or something? or if they lose and their KD and stats are TERRIBLE than lower their mmr to till they seem to fit in. I am in s2 and have got 4 matches recently with recent lvl 30's. ALL of them have either had to be carried or just fed because they are up against someone way better than them.

Other elos don't really face this. Or at least I hope they don't. maybe bronze, but that's about the equal skill cap that they are. I'm not saying as a bronze player they are that but come on. Stat wise they are horrid and being placed with people trying to make it to gold. its like sabotaging a match and giving the other team a handycap