When did people get the idea that having a 0 cs support alongside an adc was the most efficient usage of resources?
You seem to imply it's a wrong idea and that people didn't really think this through. But actually yes, it is the most efficient usage of resources.
- Empirically, at the very top level of pro-play, teams that used this strategy started to dominate and were quickly imitated, until the strategy trickled down to every Elos.
- Logically, it's better to have one fed champ (and another one providing some baseline support with the few scraps it can get) than two half-fed champs. If you have two half-fed champ, none of them can actually win a fight, it will be easy to kill one quickly and then the second one will die soon after, etc. On the other hand, if you have one fed champ, he is a big threat, and can easily 1v2 if the others aren't as fed as him, and you cannot just ignore him and focus the one that isn't fed at all, because by the time you do that, the fed one will kill you.