It's a good point, the reasoning for the jungler though is for those camps in the jungle. If you don't have a set jungler, all those camps are just extra gold just sitting there, and sure laners could go in and farm them, but there's a chance that they miss some of their own lane farm, plus camps do alot of dmg, that's why you can't have these super squishy junglers. The point behind the botlane is to have a big damage dealer be able to get gold. Sure, the same can be said for mid, but it's a shorter lane, not as much help is needed because the minions don't have as far to go. Technically you could have an apc bot and an adc mid, but it doesn't work very well with an all ad or all ap team, or at least your big damage dealers being the same, because itemization allows the other team to just mitigate more damage. The laneswaps in lcs are to get the tower down early and because the adc wants to farm with little interruption. Early game you don't see the entirety of the other team punish for a lane swap because early game farming is important, but not giving the other team kills is also important, that's why you see top lane go with the jungle for a bit to get levels to be able to get farm against the adc later on. It's too risky to play a 1v2 right at the start because the one is just going to struggle to farm against the 2 putting pressure, it hardly ever works out well. The meta is what it is because that's what the pros found work best. The early tower gives extra global gold, plus they try to set it up for a freeze to make it a farm lane for a bit afterwards.