I guess it's just the simplicity of it.
This is what I think in addition to putting it in a food processor.
Martini thinks Calvin uses a Swanson's chicken salad seasoning mix, but I contacted the company and it's no longer made.
I can make something close and get the texture close, but it's not the same and I'd rather just buy Calvin's than going through the trouble.
Like you, once I have it, I want more. I especially like having it around during tomato season. Its perfect to stuff in a tomato or an avocado for a quick summer meal. I boil some eggs and slice one to with it.