They are very two different independent systems, they complement each other, but they are not the same thing. Though, LoL Level up rewards are not to be confused with lol honor rewards. It’s important to understand the ins-and-outs of the experience system in League of Legends so you can get to those rewards sooner and level up your account the fastest. Besides the fact that you need level 30 in order to compete in ranked matches, leveling up your account to high levels unlocks numerous cosmetic and gameplay rewards that can be useful.
For every League of Legends player, new ones and old ones, leveling up is an integral part of playing the game.