Wow folks. There's a lot more to business & life than simply "fulfilling your contractual obligations". I've lived in rented small duplex/triplex-type buildings where the LL never gave so much as a "thanks for keeping the place nice", and in LARGE complexes where the management hosted annual holiday events for all the residents. Guess which management the residents treated better. Tenants can make your business easy, or a headache. Creating good will is one way to encourage (yes encourage, not guarantee) the type of behavior you want from them.
As far as scale, if your RE business cant handle a per unit $20-25 expense once a year, for client retention & good will, something is wrong.
Have you never given a holiday gift to your kids teacher, or your mailman, gardener, baby sitter, etc? All of which you've already fulfilled your "contractual obligations" to when they got paid.....doesn't mean that generating some good will is a bad idea.
We give turkeys to the residents in each unit every Thanksgiving, via our management companies.