Since when do we play like this? Why did the pros decide to play like this and why did we decide for it to be the meta? How did people in season 1/beta play before the pros invented the 1 top/jg/mid 2 bot meta?
Season 2
It's been like that since the beta. The only thing that was different prior to mid-late season 1 was some lane assignments. Top was usually a tank or a champion with so defense. If a team didn't have a support (they weren't considered mandatory at the time), the RAD (or one of the RADs) would go mid and bottom lane would be a mage and something else.
The reason it is the way it is is because it's almost certainly the most effective way to do things.
What the other guy said, it's basically always been like this, except you could get away with playing anything in any lane. We've just learned over time what does best in a solo lane / duo lane at this point, which is why we pair an ADC up with someone who can make up for their weaknesses
Why would you choose some other sub optimal way to do it?
There wasn't much to invent here because the game has 3 lanes and one jungle. The 5th player is basically the fifth wheel that has to go somewhere and Riot simply patched the game in favor of what we have now.
It came logically, allocation of resources (gold/xp), there are 3 lanes and a jungle to provide gold and XP, Marksmen scale more off of gold than levels so their sharing exp with a support is not a big problem as long as the support isn't taking the minions. In any competitive strategy game the most effective strategy at least as far as general strategy is usually found out pretty quickely, even if there are some cheese strategies than can sometimes work (duo top w/ no jg, duo jg w/ no support etc) one will always become the primary way people play because it yields the best chance of winning.
