I haven't read the whole thread, but I've read my fair share of "pool towels", "free" parking, doubling up ADRs threads this week to make my freaking head spin.
Costs aside (and I know that's a big reason for this, so don't start), why on earth do people feel they need a freaking sign or something in writing for everything? It's called EMPATHY people, look it up in the dictionary.
Whether it's the towels, doubling ADRs, using refillable mugs from the last trip, sure you CAN do it, but by skirting the rules, written down or implied, you are saying to others "to heck with everyone else, I'm the only one that matters". Seems like there are a ton of people that can spout off every "right" they have, but know nothing about their responsibilities, as a WDW guest, or even more so, as a parent.
There will always be people that think that just because they CAN do something that isn't quite against the rules kinda sorta, that they somehow are getting something for nothing. Please, don't be one of "those" people. And for the rest of us, you can only talk to "these" people so much. Most will understand, some will not. I've stopped trying to change people long ago. Just lead by example is my policy.