jungle as someone who doesn't need a leash?
If you let them start in lane every time it has the potential of giving them a slight edge against their opponents if their jungler had to get leashed. You also avoid them staying too long and stealing exp or whatever.
Also statistically you are going to be the #1 determining factor of whether or not you can climb (the enemy team has 5 slots for potential feeders/trolls/afk's your team has 4 as long as you aren't one of those). Just play more games and if you are personally better than the people at your rank you will end up pushing your winrate over 50% and start climbing. How hard you can carry even games can inflate that even more and let you climb faster.
Placements are just a starting point, and it's always more fun to start lower and climb higher (hell if you are good enough to pubstomp in low elo it is even more fun).