Yes, funny how that works and yet how people claim elo hell doesn't exist and you can carry any game if you just "get good". Some reasons for the challenge:
New players - valid reason for them being bronze/silver
People refuse to take constructive criticism - not ok; people are not toxic for telling you to ward or to NOT engage a 3v5
People are good enough to climb, but they always end up with more smurfs on the other team - this is where I get upset at smurfs. Play on smurf account, try out a new champ or build, that's all fine and good. But you shouldn't go out of your way to hard carry - this boosts bad players and holds down people who truly deserve to climb. Thus creating and reinforcing "elo hell".
Macro play - very few players have a decent understanding of macro play - most follow the famous words of Gambit Gaming - "see hero, kill hero.". This means many swings in who is winning and longer games where it is more of a toss-up and advantages can easy be turned.
Tilt - people lack macro, so they don't realize that they can easily win despite losing lane. They think they must immediately get a reply kill if they die in lane - causing them to feed rather than lose gracefully. Also causing afk, flame, and lack of teamwork in more abundance than what should be expected. There seems to be a few bottlenecks in climbing and I can attest that silver (especially low/mid silver) is one of the worst.
Troll picks - either they saw it on YouTube and have no clue why it worked, or they tried it in bots or ONE TIME in pvp and won with it. Therefore, it must be good against everything in every situation. And then it doesn't work. And they are feeding. And they are useless because their odd pick and build means they are either tanky without any damage or cc to threaten enemy team or they are all damage but die in 1.5 sec before they can make use of that damage.