I ask again: Why are Sightstone and its upgrades not getting in-field recharging?

Being forced to return to base to get new wards for Sightstone really diminishes the item's usefulness, as players are discouraged from recalling unless they're almost dead or unless they actually die. But even with all the new stuff coming for Sightstone, Riot feels it doesn't deserve to be capable of replenishing its wards in the field (for whatever reason).

Why can't Sightstone and its new upgrades get the ability to recharge wards in the field at level 9 or higher?