This is such an odd decision by a management group at a band that I wonder if customers really did complain. I can imagine an atheist/agnostic manager or just a mean sob manager who’s on a power trip being the actual source.
I am an atheist (well, a devout agnostic really, atheists have way too much certainty for my taste). My response to “have a blessed day” is invariably “And you.” I find the blessing charming and much more heartfelt than the insipid “have a nice day.”