It's a personal thing if Posties can't be arsed to cancel them, I understand that. The view I take is "I'm NOT working for free" and I consider walking up someones driveway and giving them a fivers worth of FREE stamps as "Working for FREE"
One Christmas, many moons ago when things weren't so hectic, I conducted my own little survey. I kept track of how many unfranked stamps (on letters) I'd cancelled, and a rough calculation showed I'd cancelled £200 worth over a week.
Multiply that with every postie that doesn't cancel them across the country and that's a LOT of Money. Although we all like to slag RM down at the end of the day when it comes to asking for a payrise I don't want to give then ANY excuse to say, "Well our Revenue is down so we can't afford it"!