Where is this money supposed to come from? Waiving secondary fees is a non-cash expense that is recaptured by charging those who do pay a little more. Actually paying for air, ground transportation, meals and/or lodging would easily cost up to $1,000,000 or more per year, per school, depending on how accessible the school is, and where its applicants come from. Might sound like nothing, but, trust me, it adds up, and would be recaptured, probably through increased fees charged to students.
NEVER going to happen. If this is actually a concern, virtual IIs will be the answer, not paying for something schools never paid for before.
What little money schools have for things like this is used to subsidize second looks for those with serious financial need. By then, schools have narrowed the field down to those who are already accepted, and applicants have narrowed it down to a select few finalists, since these looks are all bunched around the same few weeks, so you can realistically only attend a few, no matter how many As you are sitting on. This reduces potential costs to the schools substantially, and is not going to change.