Not just employee gifts, but nearly all gifts are valued less by the receiver than the giver.

A gift represents a decision made on behalf of the receiver by the giver. In very few situations would the receiver make the same decision as the giver with the same resources. It's assumed that the receiver will use the same resources in an optimal manner, so gift-giving is a net negative.

In some circumstances, gifts are valued higher by the receiver than the giver. Gifts of time, of expertise, of opportunity, or things that the giver can get at a much lower cost than the receiver - these can be more appreciated.

Anyway, that's my grand theory of gifting, and why I generally avoid it, unless I can make it worthwhile to the gift receiver.