Well from a purely roleplaying perspective, this also gives us some deatph about our society. I frankly have no idea how the city if Vale operates, with cultural and economical factors being made up on the spot. And while I'll always play it fast-and-loose when it comes to the realism in a RWBY Rp, by implimenting Lien into the stiry we could have our characters understand value and the importabce of wealth. While it may be "standard issue" to provide medkits, that doesnt mean theyll go for free. Someone has to pay for them. And what abiut medical procedures ? Do we have insurance? Cause even though we are hunters, we are not soldiers. Most of us are barely adults. The wounds we sustain and the damage we make has to come back in some meaningful way. 

How much money do you guys think was lost on your caravan mission? one whole truck, more then a hundred dead, more injured. All thise guards on trial. That's millions of lien lost. And the schnee company likely doesnt care because they have the money to cover it up, but can our characters say the same? Are we rich enough that lien has no value to us?