Of the 3-4 times I've been through EWR recently, the staff couldn't be bothered to interact with me at all except for bringing food. They never even offered a glass of water.

If they bothered to check in with me and offer water, sure, they've provided "service". But so long as they treat this as a purely transactional experience via the iPad, then my tip will be purely transactional. 15 seconds of work is certainly not worthy of anything over $1.