Namely, I noticed that in Star Trek: The Next Generation, holographic characters and objects can actually travel a little distance/last for a few moments outside of the holodeck. (e.g. A couple of Dixon Hill villains manage to walk outside of the holodeck in one episode, and they actually remain there for a minute before disappearing. And a snowball that Wesley throws in the holodeck during another episode travels through the holodeck door and hits Captain Picard, who's standing outside.)
But in Voyager, the moment that a holographic character/object attempts to leave the holodeck (or any other room equipped with holo-emitters), he/she/it disappears immediately. (The EMH, for example, can't step outside Sick Bay without a mobile emitter because the moment he tries to so much as stick one of his limbs through the door, the limb disappears.)
Is this discrepancy/difference ever explained in-universe? Or is it just one of those things that was changed for technical and/or aesthetic production reasons, but never really given an in-universe explanation? (Like the way that - for many years, at least - the shows' creative teams avoided giving an in-universe explanation for the physical changes made to the Klingons starting in The Next Generation.)