Why is boosting even a thing?!

I've been watching RossBoomsocks's videos on spectating Bronze and he caught two boosters apparently, so I was genuinely curious on how people even get boosted, so I Googled it, and the amount of "Professional, cheap LoL boosters" is disgusting, why hasn't riot done anything about this, or are they and I'm just not aware? Also, why do people even boost? It makes no sense to want to fight higher level people when you have no chance of winning. >.>
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