Jungle role can't use jungler items

Ok so this criticism mostly falls on people who forget to choose smite as the jungler, but it also denies the use of many tactical jungle options (ie ignite/flash Shaco)

90% of junglers cannot keep up with the game without smite/jungle item, and you outright deny the use of a jungle item to players because you cannot balance it with PvP somehow.

Most importantly, a player can select jungle and not smite and cannot buy the jungle item as the jungler. How did this get passed years of QA?