Healing stations, in comparison to medpacks are an advanced devices equipped with IFF system.
But mainly because allowing both team players to heal at any station would make Aura obsolete. While own team controls area, station is good, but as soon as enemies move in, situation will change drastically, not only opponents gain a foothold, they will be inadvertently provided with means to hold it.
In addition to that, stations provide a major boost to team that controls it, especially in defense. But with universal healthcare implemented, all attackers will have to do is to get close and whole perks of stationary healing system will be gone, since both teams will benefit from it equally, making defending team task that much harder(for their main purpose is generally to hold ground).
Altho i wouldnt mind a new feature, station hacking. Basically same idea as with C4, techs can convert it faster and if completed, then own team gain healing point. It could allow all classes, but Aura, to “own” a healing station, one at any given time, without ability to salvage/move it.