Folks in the thread have largely answered it already but there's a few reasons we stay away from support items as they exist on League-PC. Support items in this case I'm referring to (and I'm assuming you are too), the starting items for supports that assist in gold generation only. Not, stuff like Staff of Flowing waters - Normal items for support characters.
The big reasons are
- We do not need them to gold to supports early in the game. Our laning phase is shorter -and- the gold system innately accounts for it.
- We need less vision than on PC for the game to function properly. It's a smaller map with much more open terrain. We cannot mirror 1-1 ward, and vision count without very serious problems.
- We do not believe that warding is the supports job. Warding and vision gathering is part of the team nature of the game, by allowing support players to opt into buying a lot more vision, we functionally force them to buy more vision, while we want to make sure they have the opportunity to spend their gold on making their champions more powerful and better able to contribute to the team directly. You see this on early and present seasons of League on PC.