There is absolutely no reason:

For the map to not be bright as day now with the new great stealth trinket. And yet here I am in bronze with nobody upgrading it FOR ONLY 275 GOLD YOU GET UNLIMITED STEALTH WARDS, IN THEIR OWN ITEM SLOT! And can have 3 on the field at once, you don't even have to buy stealth wards anymore post 9, unless you are the jungler with a sweeper. I get tired of supports not running sightstone, then ignore you when you ask them to get it, but yet some people that play support have the nerve to ask you to build a certain way.

Let's do some quick math after level 9 if everybody bought 1 vision ward, the support got a sightstone, and everybody else upgraded trinket, you would could have 20 wards on the map at once. I know this will be ignored but I need to vent, bronze players start upgrading stealth trinket, and supports should always have sightstone. How can you safely move around the map without vision, have you ever been caught out alone in the jung moving between lanes, when you thought the enemy team was someplace else? Ever thought damn wish I knew where the enemy is, or damn if only I had known they were there I wouldn't have gone, wards can fix that. Enemy team ever gone missing, just as the dragon or baron emblem appeared on map, it's a good chance they went to it, but how can you be sure without wards, so many close games are lost because players don't ward.